Electricity (2)

Question 1

Capacitors

Answer 1

Capacitors:

• Store energy in circuits by storing electric charge, creating electric potential energy.
• Consist of two conductive plates separated by a dielectric, preventing charge flow.

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Parallel Plate Capacitor:

• Q: Charge stored on the plates.
• V: Potential difference across the plates.
• One plate holds +Q, the other –Q, with a potential difference V between them.

Question 2

Capacitance

Answer 2

Capacitance:

• Defined as the charge stored per unit potential difference.
• Units: Farads (F), often in smaller units like μF, nF, or pF.

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Capacitance Equation:

• C = Q / V where:
  
  • C = capacitance.
  • Q = charge stored.
  • V = potential difference.

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Key Points:

• Charge stored refers to the magnitude of charge on each plate or surface of a spherical conductor.
• Higher capacitance means the capacitor can store more charge for the same potential difference.

Question 3

Use of capacitors

Answer 3

• Energy storage: Capacitors store electric potential energy for various applications.
• Camera flashes: Provide a bright flash of light during discharge.
• Smoothing currents: Stabilize current in electronic circuits.
• Backup power: Supply power during unexpected outages for memory devices like calculators.
• Timing circuits: Used in electronic timers for precise operations.

Question 4

Charging capacitor

Answer 4

1. Initial Setup:
   
   • A circuit with a battery (e.m.f. ε), resistor (R), capacitor (C), and switch connected in series.
2. Switch Closed:
   
   • Electrons flow from the negative terminal of the battery, through the resistor, to the negative plate of the capacitor.
3. Plate Charging:
   
   • The positive terminal pulls electrons from one plate, leaving it positively charged.
   • The negative terminal pushes electrons onto the other plate, making it negatively charged.
4. Insulator Role:
   
   • The insulator between the plates prevents charge flow, forcing charge to accumulate.
5. Electrostatic Repulsion:
   
   • As negative charge builds, it repels incoming electrons, slowing the flow of charge.
6. Current and Voltage:
   
   • Current decreases exponentially over time.
   • Potential difference (V) across the plates increases as charge accumulates, eventually matching the supply voltage.
7. Fully Charged:
   
   • The capacitor stops charging when it reaches maximum charge, determined by its capacitance (C) and the supply voltage.

Question 5

Discharging Capacitors

Answer 5

1. Initial Setup:
   
   • A circuit with a resistor (R), switch, and capacitor (C) in series. No power supply is present.
2. Switch Closed:
   
   • The potential difference (V) across the capacitor causes a current (I) to flow through the circuit.
3. Current Flow:
   
   • Electrons flow from the negative plate of the capacitor, through the resistor, to the positive plate, reducing charge on both plates.
4. Exponential Decay:
   
   • Current, potential difference, and charge decrease exponentially over time.
   • The rate of decrease is proportional to the amount remaining.
5. Discharge Completion:
   
   • The capacitor is fully discharged when potential difference (V) and current (I) fall to zero.
6. Energy Dissipation:
   
   • The electrical energy stored in the capacitor is transferred to thermal energy in the resistor.
7. Graphs:
   
   • Current, potential difference, and charge follow an identical exponential decay pattern over time.

Question 6

Energy Stored by a Capacitor

Answer 6

Charge and Potential Difference:

• Charge (Q) is directly proportional to the potential difference (V), forming a straight-line graph.

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Energy Stored:

• The electrical energy stored in the capacitor is represented by the area under the potential-charge graph, forming a triangle.

Question 7

Capacitors in Series

Answer 7

1. Charge and Potential Difference:
   
   • The potential difference (p.d.) is shared between capacitors, but each stores the same charge (Q).
   • A negative charge on the left plate of C₁ induces an equal positive charge on its right plate.
   • This causes a negative charge on the left plate of C₂, equal to the positive charge on its right plate.
2. Total Potential Difference:
   
   • V_total = V₁ + V₂
   • Substituting V = Q/C
     V_total = (Q/C₁) + (Q/C₂)
3. Total Capacitance:
   
   • Since current (and charge Q) is the same in series, Q cancels out:
     1/C_total = (1/C₁) + (1/C₂)

Question 8

Capacitors in Parallel

Answer 8

1. Potential Difference:
   
   • All capacitors have the same potential difference (p.d.) across them.
2. Charge Distribution:
   
   • The current splits across each junction, so the charge stored on each capacitor is different.
   • The total charge (Q) is the sum of the charges on each capacitor:
     Q = Q₁ + Q₂.
3. Charge on Each Capacitor:
   Q₁ = C₁V and Q₂ = C₂ V, where V is the common p.d.
   
   • Therefore, Q_total = (C₁ + C₂) V
4. Total Capacitance:
   
   • C_total = C₁ + C₂ + C₃ + ….

Question 9

Time Constant

Answer 9

Time to Half (t_1/2):

• The time it takes for the charge, current, or voltage of a discharging capacitor to decrease to half its initial value.
• Equation: t_1/2 = ln(2) τ

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Time Constant (τ):

• Measures how long it takes for the charge, current, or voltage of a discharging capacitor to decrease to 37% of its original value, or for a charging capacitor to rise to 63% of its maximum value.
• Equation: τ = RC where:
  
  • R = resistance (Ω).
  • C = capacitance (F).

Question 10

How to verify if potential difference (V) or charge (Q) on a capacitor decreases exponentially?

Answer 10

Constant ratio method:

• Plot a V-T graph and check if the time constant is constant,
• when t = τ the potential difference on the capacitor will have decreased to approximately 37% of its original value

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Logarithmic graph method

• Plot a graph of ln(V )against time (t) and check if a straight-line graph is obtained.

Question 11

Charging and Discharging graphs

Answer 11

Charging Graphs:

1. p.d. and Charge vs. Time:
   
   • Both graphs have identical shapes, starting at 0 and increasing to a maximum value.
2. Current vs. Time:
   
   • An exponential decay curve, starting at 0 and decreasing exponentially.

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Discharge Graphs:

1. Current, p.d., and Charge vs. Time:
   
   • All graphs show exponential decay curves with decreasing gradients.
   • Initial values (I₀, V₀, Q₀) start on the y-axis and decrease exponentially.
2. Rate of Discharge:
   
   • High resistance: Slower discharge, current decreases, capacitor discharges slowly.
   • Low resistance: Faster discharge, current increases, capacitor discharges quickly.

Question 12

Electric field

Answer 12

A region where a unit charge experiences an electrostatic force.

Question 13

Electric Field Lines In a uniform electric field

Answer 13

Uniform Electric Field:

• Field lines are equally spaced at all points.
• Electric field strength is constant at all points.
• The force on a test charge has the same magnitude and direction everywhere.

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Electric Field Between Parallel Plates:

• When a potential difference is applied, the plates become charged.
• The electric field between the plates is uniform.
• The field beyond the edges is non-uniform.
• Field lines are directed from the positive to the negative plate.
• A uniform electric field has equally spaced field lines.

Question 14

Electric Field Lines In a radial electric field:

Answer 14

Radial Electric Field:

• Field lines are equally spaced near the charge but spread out with distance.
• Electric field strength and force on a test charge decrease with distance from the charge.

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Around a Point Charge:

• The field is radial, with lines:
  
  • Radially inwards for negative charges.
  • Radially outwards for positive charges.

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Field Strength:

• The field is stronger where lines are closer together and weaker where lines are further apart.

Question 15

Electric Field Strength

Answer 15

• Electrostatic force per unit positive charge
• acting on a charge at a specific point
• or on a stationary point charge

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• Describes how strong or weak an electric field is

Question 16

Coulomb’s Law

Answer 16

Electric Fields and Coulomb’s Law:

• All charged particles produce an electric field, exerting a force on other charges within range.

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Coulomb’s Law:

• The force between two charges is:
  
  • Proportional to the product of their charges (Qq).
  • Inversely proportional to the square of their separation (r²).

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Charge Interactions:

• Like charges (Qq > 0) Repulsion.
• Opposite charges (Qq < 0) Attraction.

Question 17

Electric Field strength of a Point Charge

Answer 17

Radial Field

• Charged sphere acts as a point charge
• Follows an inverse square law (1/r²)

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Direction

• Towards a negative charge
• Away from a positive charge.

Question 18

Electric Field Strength in a Uniform Field

Answer 18

Electric Field Strength in a Uniform Field:

• Equation: E = V/d
  where:
  
  • E = electric field strength.
  • V = potential difference.
  • d = distance between plates.

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Key Points:

• Greater voltage (V): Results in a stronger field (E).
• Greater separation (d): Results in a weaker field (E).
• Does not apply to a radial field around a point charge.
• Field direction: From the positive to the negative plate.

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Derivation:

1. Work done on a charge ( Q ):
   W = ΔV × Q
2. Work done as force × distance:
   W = F × d
3. Equating the two:
   F × d = ΔV × Q.
4. Rearranging:
   F/Q = ΔV/d.
5. Since E = F/Q
   E = ΔV/d.

Question 19

Relative permittivity

Answer 19

Permittivity:

• Measures how easy it is to generate an electric field in a material.

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Relative permittivity (εr) (dielectric constant)

• ratio of permittivity of a material to permittivity of free space (ε0):
• εr = ε/ε0.
• Dimensionless because it’s a ratio of two quantities with the same unit.

Question 20

Effect of Dielectric on Capacitance

Answer 20

Dielectric in a Capacitor:

1. Polar Molecules:
   
   • Align with the applied electric field, creating an opposing electric field.
   • This reduces the overall electric field, lowering the potential difference between the plates.
2. Permittivity:
   
   • Reflects how well polar molecules align with the field; higher alignment = higher permittivity.
3. Parallel Plate Capacitor:
   
   • Plates of area A, separated by distance d, with a dielectric of permittivity ε between them.
   • The reduction in potential difference increases the capacitance of the plates.

Question 21

Motion of Charged Particles in an Electric Field

Answer 21

Charged Particles in an Electric Field:

1. Force and Motion:
   
   • Charged particles experience a force, causing them to move.
   • In a uniform electric field, particles move parallel to the field lines (direction depends on charge).
2. Perpendicular Motion:
   
   • A particle moving perpendicular to the field follows a parabolic trajectory due to the constant force.
3. Deflection:
   
   • Positive charges: Deflect towards the negative plate.
   • Negative charges: Deflect towards the positive plate.
   • Deflection depends on mass, charge, and speed:
     
     • Heavier particles deflect less.
     • Larger charges and slower particles deflect more.

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Formulas:

• Force: F = EQ
• Work Done: W = Fd
• Kinetic Energy: The force increases the particle’s kinetic energy, causing constant acceleration (Newton’s second law).
• Perpendicular Velocity: If the particle’s velocity has a component perpendicular to the field, it remains unchanged (Newton’s first law).

Question 22

Electric Potential

Answer 22

Electric Potential:

• Defined as the work done per unit positive charge to bring a test charge from infinity to a defined point.
• A scalar quantity (no direction) but can be positive, negative, or zero:
  
  • Positive around an isolated positive charge.
  • Negative around an isolated negative charge.
  • Zero at infinity.

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Total Electric Potential:

• The total potential at a point from multiple charges is the sum of the potentials from each individual charge.

Question 23

The graph of potential V against distance r for a negative or positive charge

Answer 23

Electric Potential for a Positive Charge:

• As distance (r) decreases, electric potential (V) increases.
• More work is required to overcome the repulsive force as the test charge moves closer.
• V starts positive and increases as r decreases, approaching zero as r approaches infinity.

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Electric Potential for a Negative Charge:

• As distance (r) decreases, electric potential (V) decreases (becomes more negative).
• Less work is required due to the attractive force, which pulls the test charge closer.
• V starts negative and decreases (in magnitude) as r decreases, approaching zero as r increases towards infinity.

Question 24

Electric Potential Energy

Answer 24

Work in an Uniform Electric Field:

• Work is done when a charge moves through an electric field.
  
  • Positive charge: Work is done when it moves against the field.
  • Negative charge: Work is done when it moves with the field.

Key Points

• The work done equals the change in electric potential energy.
• When the electric potential is zero, the electric potential energy is also zero.
• The work done depends on the distance the charge moves in the field.
• q = charge being moved; Q = charge producing the potential. Do not confuse the two in calculations.

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Work in a Radial Field:

• Work is required to:
  
  • Move a positive charge closer to another positive charge (overcoming repulsion).
  • Move a positive charge away from a negative charge (overcoming attraction).

Key points

• Potential energy increases when moving a charge towards a repelling charge and decreases when moving away from an attracting charge.

Question 25

Force-Distance Graph for a Point Charge

Answer 25

Force-Distance Graph:

• Force (F) values are all positive.
• As r increases, F follows a 1/r² relation (inverse square law).
• The area under the graph represents work done (ΔW).
• The graph shows a steep decline as r increases.

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Estimating Area:

• Use methods like counting squares or summing areas of trapeziums.

Question 26

Electric field between two point charges

Answer 26

Opposite Charges:

• Field lines are directed from the positive charge to the negative charge.
• As the charges get closer, the attractive force becomes stronger.

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Same Type Charges:

• Field lines are directed away from two positive charges or towards two negative charges.
• As the charges get closer, the repulsive force becomes stronger.
• A neutral point exists at the midpoint where the resultant electric force is zero.

Question 27

Capacitance of an Isolated Sphere

Answer 27

Capacitance of a Charged Sphere:

• Defined as the charge per unit potential at the surface:
  C = Q / V

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Key Equations:

1. Potential of an Isolated Point Charge:
   V = Q / (4πε₀R)
2. Capacitance of an Isolated Sphere:
   C = 4πε₀R

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Variables:

• Q = charge on the sphere (considered as a point charge at its center).
• R = radius of the sphere.
• ε₀ = permittivity of free space.

Question 28

Electric Fields vs Gravitational Fields

Answer 28

Similarities Between Gravitational and Electrostatic Forces:

1. Both follow the inverse square law.
2. Field lines around a point mass and a negative point charge are identical.
3. Field lines in uniform gravitational and electric fields are identical.
4. Field strengths in a radial field have a 1/r relationship.
5. Potential in both fields has a 1/r relationship.
6. Equipotential surfaces are:
   
   • Spherical around a point mass or charge.
   • Parallel in uniform fields.
7. Work done is the product of:
   
   • Mass and change in gravitational potential.
   • Charge and change in electric potential.

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Differences:

1. Gravitational force acts on mass; electrostatic force acts on charge.
2. Gravitational force is always attractive; electrostatic force can be attractive or repulsive.
3. Gravitational potential is always negative; electric potential can be negative or positive.

Question 29

Magnetic Fields

Answer 29

Magnetic Field:

• A field of force created by moving electric charges or permanent magnets, also called a B-field.

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Sources of Magnetic Fields:

• Permanent magnets produce magnetic fields.
• Current-carrying wires create magnetic fields due to the movement of electrons (stationary charges do not produce magnetic fields).

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Observing Magnetic Fields:

• Although invisible, their effects can be observed through:
  
  • The force acting on magnetic materials (e.g., iron).
  • The movement of a needle in a plotting compass.

Question 30

Field Lines in a Current-Carrying Wire

Answer 30

Magnetic Field Around a Current-Carrying Wire:

• Field lines are circular rings centered on the wire.
• The field is strongest near the wire and weakens with distance.
• Reversing the current reverses the direction of the field lines.

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Maxwell’s Right-Hand Screw Rule:

• Point your thumb in the direction of the conventional current (positive to negative).
• The curled fingers indicate the direction of the magnetic field around the wire.

Question 31

Magnetic Field Lines in Solenoids and Coils

Answer 31

Field Lines in a Solenoid:

• Electromagnets use solenoids (coils of wire) to concentrate magnetic fields.
• One end becomes the north pole, and the other becomes the south pole.
• Magnetic field lines resemble those of a bar magnet:
  
  • Emerge from the north pole.
  • Return to the south pole.

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Field Lines in a Flat Circular Coil:

• Behaves like a single loop of a solenoid.
• Field lines:
  
  • Emerge from one side (north pole).
  • Return to the other side (south pole).
• Multiple coils in a solenoid combine to create a stronger, uniform field.

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Right-hand thumb rule:
- Thumb shows the magnetic field direction.
- Fingers show the current direction.

Question 32

Factors Affecting the Magnetic Field Strength

Answer 32

1. Add a Ferrous Core:
   
   • Use a core made from a ferrous (iron-rich) material (e.g., an iron rod).
   • When current flows, the core becomes magnetised, increasing the field strength by several hundred times.
2. Add More Turns to the Coil:
   
   • Concentrates the magnetic field lines, increasing the field strength.

Question 33

Fleming’s Left-Hand Rule

Answer 33

Fleming’s Left-Hand Rule:

• Determines the direction of magnetic force on a moving charged particle in a magnetic field:
  
  • First Finger: Direction of the magnetic field.
  • Second Finger: Direction of conventional current (velocity of a moving positive charge).
  • Thumb: Direction of the magnetic force.

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Magnetic Field Direction in 3D:

• Dots (tip of an arrow): Magnetic field coming out of the page.
• Crosses (back of an arrow): Magnetic field going into the page.

Question 34

Magnetic Flux Density

Answer 34

• Defined as the force acting per unit current per unit length on a current-carrying conductor placed perpendicular to the magnetic field.
• Units: Tesla (T), where 1 T = 1 N m⁻¹ force on a conductor carrying 1 A current normal to the field.
• Also referred to as magnetic field strength.

Question 35

Force on a Current-Carrying Conductor

Answer 35

Magnetic Force on a Current-Carrying Conductor:

• A current-carrying conductor produces its own magnetic field.
• An external magnetic field exerts a magnetic force on the conductor.
• The maximum force occurs when the current is perpendicular to the magnetic flux lines.

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Magnitude of Magnetic Force (F):

• Proportional to:
  
  • Current (I).
  • Magnetic flux density (B).
  • Length of conductor in the field (L).
  • Sine of the angle (θ) between the conductor and the magnetic flux lines.
• No force is experienced if the current is parallel to the magnetic field.

Question 36

Force on a Moving Charge

Answer 36

Magnetic Force on a Moving Charged Particle:

• Equation: F = BQv, where:
  
  • F = magnetic force (N).
  • B = magnetic flux density (T).
  • Q = charge of the particle (C).
  • v = speed of the particle (m/s).
• This is the maximum force when F, B, and v are mutually perpendicular.
• If the particle travels parallel to the magnetic field, it does not experience a magnetic force.

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Force at an Angle θ:

• When the particle moves at an angle θ to the magnetic field lines:
  F = BQv sin θ

Question 37

Motion of a Charged Particle in a Magnetic Field

Answer 37

Circular Motion of a Charged Particle in a Magnetic Field:

• A charged particle in a uniform magnetic field perpendicular to its motion travels in a circular path because:
  
  • The magnetic force (F) is always perpendicular to its velocity (v), causing circular motion.
  • The magnetic force always points towards the center of the circular path.

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Centripetal Force:

• Provides the force required for circular motion:
  mv² / r = BQv
• Rearranging for the radius r:
  r = mv / BQ

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Key Points:

• Faster particles (v): Move in larger circles r ∝ v
• Greater mass (m): Move in larger circles r ∝ m
• Greater charge (q): Move in smaller circles r ∝ 1 / q
• ## Stronger magnetic field (B): Move in smaller circles r ∝ 1 / B

• Calculated using Newton’s second law:
  F = ma

Question 38

Charged Particles in a Velocity Selector

Answer 38

Velocity Selector:

• Filters charged particles by using perpendicular electric and magnetic fields to allow only particles with a specific velocity to pass through.
• Used in devices like mass spectrometers to create a beam of particles moving at the same speed.

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Setup:

• Two oppositely charged plates create an electric field (E).
• A magnetic field (B) is applied perpendicular to the electric field.

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Force Balance:

• Electric force: F_E = EQ (independent of velocity).
• Magnetic force: F_B = BQv (depends on velocity).
• For a particle to pass through undeflected, the forces must balance:
  F_E = F_B.
• The selected velocity is:
  v = E / B.

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Deflection:

• Particles with velocities different from v are deflected and removed from the beam.

Question 39

Magnetic Flux

Answer 39

Magnetic Flux (Φ):

• Defined as the product of magnetic flux density (B) and the cross-sectional area (A) perpendicular to the magnetic field:
  Φ = B A
• Units: Webers (Wb).

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Key Points:

• Maximum flux: Occurs when the magnetic field lines are perpendicular to the area.
• Minimum flux: Occurs when the magnetic field lines are parallel to the area.
• Represents the amount of magnetic field passing through a given area.

Question 40

Magnetic Flux Linkage

Answer 40

Magnetic Flux Linkage:

• Commonly used for solenoids with N turns of wire.
• Defined as the product of magnetic flux (Φ) and the number of turns (N) in the coil:
  ΦN = Φ × N = B × A × N** where:
  
  • B = magnetic flux density.
  • A = cross-sectional area of the coil.
  • N = number of turns in the coil.
• Units: Weber turns (Wb turns).

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General Equation:

-ΦN = B × A × N × cos(θ) where θ is the angle between the magnetic field lines and the normal to the coil.

Question 41

Faraday’s Law

Answer 41

• The magnitude of the induced e.m.f. (electromotive force) is directly proportional to the rate of change of magnetic flux linkage.
• The equation form of Faraday’s Law is:
  ε = Δ(Nɸ) / Δt
  Where:
  
  • ε = induced e.m.f (V)
  • Δ(Nɸ) = change in flux linkage (Wb turns)
  • Δt = time interval (s)

Question 42

Lenz’s Law

Answer 42

Lenz’s Law:

• The induced e.m.f. produces effects that oppose the change causing it.

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Example:

• If a north pole approaches the coil, the induced e.m.f. creates an opposing north pole to repel the incoming magnet.

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Right-Hand Grip Rule:

• Curl fingers around the coil in the direction of the current.
• The thumb points along the direction of the magnetic flux (north to south).
• In this case, the current flows anti-clockwise, inducing a north pole to oppose the incoming magnet.

Question 43

Induced E.m.f.

Answer 43

Faraday’s Law with Lenz’s Law:

The equation that combines Faraday’s Law and Lenz’s Law is written as:
ε = - Δ(Nɸ) / Δt

• The negative sign represents Lenz’s Law.

Question 44

EMF Inducted in a Rotating Coil

Answer 44

Induced E.M.F. in a Rotating Coil:

• When a coil rotates in a uniform magnetic field, the magnetic flux through the coil changes, causing the induced e.m.f. to change.
• The e.m.f. is:
  
  • Maximum when the coil cuts through the most magnetic field lines (normal to the coil is perpendicular to the field).
  • Zero when the coil is aligned with the field (normal to the coil is parallel to the field).

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E.M.F. Formula:

• ε = BANω sin(θ)
• where θ = ωt
• The e.m.f. varies sinusoidally and is 90° out of phase with the flux linkage.

Question 45

Alternators

Answer 45

Alternator:

• A device that converts mechanical energy into electrical energy using a rotating coil in a magnetic field.

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Components:

1. Coil: A rectangular coil rotates within a uniform magnetic field, generating electricity.
2. Slip Rings: Metal rings that rotate with the coil, maintaining continuous electrical contact.
3. Brushes: Metal brushes press against the slip rings to transfer current to the external circuit.

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Operation:

• As the coil rotates, it cuts through magnetic field lines, inducing a potential difference (voltage) across the coil.
• The induced current changes direction as the coil spins, creating an alternating current (AC).
• The meter pointer deflects first in one direction, then the opposite, as the current reverses.
• The induced voltage and current alternate direction continuously, producing a steady AC waveform.

Question 46

Dynamos

Answer 46

Dynamo:

• A direct-current (D.C.) generator that uses a split-ring commutator instead of slip rings.
• Consists of a rotating coil in a magnetic field.

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Operation:

• The split-ring commutator ensures the current stays in one direction.
• The induced potential difference varies only in the positive region of the graph, never reversing direction.
• The current is always positive (or negative), never alternating.

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Key Process:

• As the coil rotates, it cuts through magnetic field lines, inducing a potential difference between the coil’s ends.
• The split-ring commutator changes the coil’s connection to the brushes every half turn, keeping the current in the same direction.
• This change occurs when the coil is perpendicular to the magnetic field lines.

Question 47

Transformer Basics

Answer 47

Transformer:

• Changes high alternating voltage at low current to low alternating voltage at high current, and vice versa.
• Increases transmission efficiency by reducing heat energy loss in power lines.

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Power Loss:

• Given by P = I²R, so reducing current reduces power loss during transmission.

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Applications:

• Used in the National Grid for efficient power transmission.
• Step-up transformers: Increase voltage and decrease current for long-distance transmission.
• Step-down transformers: Reduce voltage and increase current for local use near homes and businesses.

Question 48

Transformer Components and Functioning

Answer 48

Step-Up Transformer:

• The secondary coil has more turns than the primary coil, increasing voltage.

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Operation:

• The primary coil is powered by an alternating current (AC), creating a changing magnetic field in the iron core.
• The changing magnetic field induces an e.m.f. in the secondary coil.
• The secondary voltage depends on the number of turns:
  
  • More turns = step-up (voltage increases).
  • Fewer turns = step-down (voltage decreases).

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Components:

• Primary coil, secondary coil, and soft iron core.
• The soft iron core focuses and directs the magnetic field between the coils, and is used because it can be easily magnetised and demagnetised.

Question 49

Eddy Currents

Answer 49

Transformer Efficiency:

• Transformers are not 100% efficient, and power loss occurs due to various factors.

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Eddy Currents:

• Looping currents in the core caused by the changing magnetic flux.
• Effects:
  
  • Generate heat, leading to energy loss.
  • Create a magnetic field that opposes the inducing field, reducing field strength.

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Reducing Eddy Currents:

• The core is laminated, with layers separated by thin insulating material to prevent current flow.