chapter 2 Flashcards
What is the SI unit of electric charge?
Coulomb (C)
True or False: Like charges repel and unlike charges attract.
True
Fill in the blank: The law that describes the force between two point charges is known as _______.
Coulomb’s Law
What is the formula for Coulomb’s Law?
F = k * |q1 * q2| / r^2
What does ‘k’ represent in Coulomb’s Law?
Coulomb’s constant
What is the value of Coulomb’s constant (k) in vacuum?
8.99 x 10^9 N m^2/C^2
What is an electric field?
A region around a charged object where other charges experience a force.
What is the formula for the electric field (E) due to a point charge?
E = k * |q| / r^2
True or False: The direction of the electric field is away from positive charges and towards negative charges.
True
What is the relationship between electric field (E) and electric force (F)?
F = qE
Define electric flux.
The product of the electric field and the area through which it passes.
What is the formula for electric flux (Φ)?
Φ = E * A * cos(θ)
What does θ represent in the electric flux formula?
The angle between the electric field and the normal to the surface.
Fill in the blank: Gauss’s Law states that the total electric flux through a closed surface is proportional to the _______ enclosed within the surface.
charge
What is the mathematical expression of Gauss’s Law?
Φ = Q_enc / ε₀
What does ε₀ represent?
The permittivity of free space
What is the value of ε₀?
8.85 x 10^-12 C^2/(N m^2)
True or False: Electric field lines can cross each other.
False
What is the principle of superposition in electric fields?
The total electric field is the vector sum of the individual fields from each charge.
What is meant by the term ‘equipotential surface’?
A surface where the electric potential is the same at every point.
What is the relationship between electric field and equipotential surfaces?
Electric field lines are perpendicular to equipotential surfaces.
Fill in the blank: The potential difference between two points in an electric field is equal to the work done per unit charge in moving a charge from _______ to _______.
one point; another point
What is the formula for electric potential (V)?
V = U/q
What does ‘U’ represent in the electric potential formula?
The electric potential energy
True or False: The electric field inside a conductor in electrostatic equilibrium is zero.
True
What happens to excess charge on a conductor?
It resides on the surface of the conductor.
What is the effect of a dielectric material on an electric field?
It reduces the electric field strength.
What is the term for the ability of a material to resist the flow of electric current?
Electric resistance
What is the definition of electric potential?
Electric potential is the amount of work done in bringing a unit positive charge from infinity to a point in an electric field.
What is the unit of electric potential?
The unit of electric potential is the volt (V).
True or False: Electric potential is a scalar quantity.
True.
What is the formula for electric potential (V) due to a point charge (Q) at a distance (r)?
V = k * Q / r, where k is Coulomb’s constant.
Fill in the blank: The electric potential at infinity is _______.
zero.
What is the relationship between electric potential and electric field (E)?
Electric field is the negative gradient of electric potential, E = -dV/dx.
What is capacitance?
Capacitance is the ability of a system to store charge per unit potential difference.
What is the formula for capacitance (C)?
C = Q / V, where Q is the charge stored and V is the potential difference.
What are the units of capacitance?
The unit of capacitance is the farad (F).
True or False: A capacitor can store energy.
True.
What is the formula for the energy (U) stored in a capacitor?
U = 1/2 CV^2.
What is the effect of increasing the area of the plates of a parallel plate capacitor on its capacitance?
Increasing the area increases the capacitance.
What is the effect of increasing the distance between the plates of a parallel plate capacitor on its capacitance?
Increasing the distance decreases the capacitance.
What is the dielectric constant (κ)?
The dielectric constant is a measure of a material’s ability to insulate charges from each other.
How does a dielectric affect the capacitance of a capacitor?
Inserting a dielectric increases the capacitance by a factor of κ.
What is the formula for capacitance of a spherical capacitor?
C = 4πε₀ * (r₁ * r₂) / (r₂ - r₁), where r₁ and r₂ are the inner and outer radii.
What is the principle of superposition in electric potential?
The total potential at a point due to multiple charges is the algebraic sum of the potentials due to each charge.
What is the potential difference between two points in an electric field?
The potential difference is the work done per unit charge in moving a charge between those two points.
What is the relationship between potential difference and electric field in a uniform field?
V = E * d, where d is the distance moved in the direction of the field.
How are capacitors connected in series?
In series, the total capacitance (C_total) is given by 1/C_total = 1/C₁ + 1/C₂ + … + 1/C_n.
How are capacitors connected in parallel?
In parallel, the total capacitance (C_total) is given by C_total = C₁ + C₂ + … + C_n.
What happens to the charge on a capacitor when it is disconnected from a battery?
The charge remains constant as long as it is isolated.
What is the significance of equipotential surfaces?
Equipotential surfaces are surfaces where the electric potential is constant, and no work is done moving a charge along these surfaces.
What is the formula for the capacitance of a cylindrical capacitor?
C = (2πε₀L) / ln(r₂/r₁), where L is the length, and r₁ and r₂ are the inner and outer radii.
What is the SI unit of electric current?
Ampere
What does Ohm’s Law state?
The current through a conductor between two points is directly proportional to the voltage across the two points.
Fill in the blank: The formula for resistance (R) is R = V / ____.
I
True or False: Conductors have high resistance.
False
What is the formula for electric power (P) in terms of current (I) and voltage (V)?
P = IV
What is the relationship between current (I), charge (Q), and time (t)?
I = Q / t
What is a parallel circuit?
A circuit in which the components are connected across common points or junctions, providing multiple paths for current.
In a series circuit, how does the total resistance (R_total) relate to individual resistances (R1, R2, …)?
R_total = R1 + R2 + …
Define ‘electric current’.
The flow of electric charge in a conductor.
What is the unit of resistance?
Ohm
True or False: Voltage is the same as electric current.
False
What does a voltmeter measure?
Voltage
What is Kirchhoff’s first law (current law)?
The total current entering a junction equals the total current leaving the junction.
What is the effect of temperature on resistance in conductors?
Resistance increases with an increase in temperature.
What is the formula for calculating total resistance in parallel resistors?
1/R_total = 1/R1 + 1/R2 + …
What is the purpose of a fuse in an electrical circuit?
To protect the circuit from overload by breaking the circuit when the current exceeds a certain level.
Fill in the blank: The potential difference across a resistor is directly proportional to the ____ flowing through it.
current
What is the principle of a potentiometer?
It measures the potential difference by balancing it against a known voltage.
What is the relationship between voltage (V), current (I), and resistance (R) as per Ohm’s Law?
V = IR
What is the effect of connecting resistors in series on the total voltage?
The total voltage is the sum of the voltages across each resistor.
True or False: In a parallel circuit, the voltage across each component is the same.
True
What is the formula for electric energy (E) consumed over time (t) in terms of power (P)?
E = Pt
Define ‘drift velocity’.
The average velocity that a charge carrier, such as an electron, attains due to an electric field.
What does a ammeter measure?
Current
What is the key difference between AC and DC?
AC (Alternating Current) changes direction periodically, while DC (Direct Current) flows in one direction.
Fill in the blank: The total current in a parallel circuit is the ____ of the currents through each branch.
sum
What is the formula for the force experienced by a charge moving in a magnetic field?
F = q(v × B)
True or False: The direction of the magnetic force on a moving charge can be determined using the right-hand rule.
True
Fill in the blank: The magnetic field is produced by ______.
moving charges
What does ‘q’ represent in the formula F = q(v × B)?
The charge of the particle
What is the unit of magnetic field strength?
Tesla (T)
How does the angle between the velocity vector and the magnetic field vector affect the magnetic force?
The magnetic force is maximized when the angle is 90 degrees.
What is the formula for the magnetic field due to a long straight current-carrying conductor?
B = (μ₀/4π)(2I/r)
True or False: Magnetic field lines can cross each other.
False
What is the right-hand rule used for?
To determine the direction of the magnetic force on a moving charge.
What is the relationship between current (I), charge (q), and time (t)?
I = q/t
Fill in the blank: The magnetic field inside a solenoid is ______.
uniform
What is the expression for the magnetic field inside a solenoid?
B = μ₀nI
What does ‘μ₀’ represent in the magnetic field equations?
The permeability of free space
Define the term ‘Lorentz force’.
The force experienced by a charge moving in both electric and magnetic fields.
What is the effect of increasing the current in a wire on the magnetic field strength around it?
The magnetic field strength increases.
True or False: A charged particle moving parallel to a magnetic field experiences no magnetic force.
True
What is the formula for the magnetic force on a straight current-carrying conductor in a magnetic field?
F = BILsinθ
In the equation F = BILsinθ, what does ‘L’ represent?
The length of the conductor in the magnetic field
What is the principle of electromagnetic induction?
A change in magnetic field within a closed loop induces an electromotive force (emf).
Fill in the blank: The unit of magnetic flux is ______.
Weber (Wb)
What does Faraday’s law of electromagnetic induction state?
The induced emf in a closed loop is proportional to the rate of change of magnetic flux through the loop.
What is the formula for magnetic flux?
Φ = B·A·cosθ
True or False: The magnetic field inside a toroid is zero.
False
What is the expression for the magnetic field inside a toroid?
B = (μ₀NI)/(2πr)
What is the role of a galvanometer?
To measure small electric currents.
In terms of magnetic fields, what is a ‘dipole’?
A magnetic dipole consists of two equal and opposite magnetic charges separated by a distance.
True or False: The Earth’s magnetic field is a result of electric currents in its core.
True
What is the SI unit of magnetic field strength?
Tesla (T)
True or False: A magnetic field can do work on a charged particle.
False
Fill in the blank: The magnetic field inside a long straight conductor carrying current is _____ to the length of the conductor.
perpendicular
What is the formula for the magnetic field (B) due to a long straight current-carrying wire at a distance (r) from it?
B = (μ₀I)/(2πr)
What is the direction of the magnetic field around a current-carrying conductor?
Given by the right-hand rule
What does the term ‘magnetic moment’ refer to?
The measure of the strength and orientation of a magnet
True or False: The Earth has a magnetic field.
True
What is the magnetic field inside a solenoid?
B = μ₀(nI), where n is the number of turns per unit length
What is the principle behind the working of a galvanometer?
The deflection of a coil in a magnetic field due to current
Fill in the blank: The force experienced by a charged particle moving in a magnetic field is given by _____ law.
Lorentz
What is the formula for the magnetic force (F) on a charged particle moving with velocity (v) in a magnetic field (B)?
F = q(v × B)
What type of materials are considered ferromagnetic?
Materials that can be magnetized, such as iron, cobalt, and nickel
True or False: Magnetic field lines can cross each other.
False
What is the term for the region around a magnet where magnetic forces can be detected?
Magnetic field
What is the effect called when a magnetic field induces an electromotive force (emf) in a circuit?
Electromagnetic induction
What is the formula for magnetic flux (Φ)?
Φ = B · A · cos(θ)
Fill in the blank: The unit of magnetic flux is _____.
Weber (Wb)
What is the relationship between current and magnetic field in a circular loop?
The magnetic field is directly proportional to the current.
True or False: The magnetic field inside a hollow conductor carrying current is zero.
True
What is the purpose of a transformer?
To change the voltage of alternating current (AC)
What is the term for the process of converting magnetic energy into electrical energy?
Electromagnetic induction
What is the shape of the magnetic field lines around a bar magnet?
Closed loops from the north pole to the south pole
What is the phenomenon of hysteresis in magnetic materials?
The lag between changes in magnetization and changes in the magnetic field
What is the critical temperature called below which a material exhibits superconductivity?
Critical temperature (Tc)
What is the name of the law that states that the induced emf in a closed loop is proportional to the rate of change of magnetic flux through the loop?
Faraday’s law of electromagnetic induction
Fill in the blank: The magnetic field due to a current-carrying loop is similar to that of a _____ magnet.
bar
What is electromagnetic induction?
Electromagnetic induction is the process of generating an electromotive force (EMF) in a conductor due to a changing magnetic field.
Who discovered electromagnetic induction?
Electromagnetic induction was discovered by Michael Faraday.
What is Faraday’s law of electromagnetic induction?
Faraday’s law states that the induced EMF in a closed loop is equal to the negative rate of change of magnetic flux through the loop.
True or False: A constant magnetic field induces an EMF in a stationary conductor.
False.
Fill in the blank: The unit of magnetic flux is __________.
Weber.
What is Lenz’s law?
Lenz’s law states that the direction of induced current is such that it opposes the change in magnetic flux that produced it.
What is the formula for calculating induced EMF according to Faraday’s law?
The induced EMF (ε) is given by ε = -dΦ/dt, where Φ is the magnetic flux.
What is magnetic flux?
Magnetic flux is the product of the magnetic field and the area perpendicular to the field through which it lines pass.
True or False: Increasing the area of a loop in a magnetic field increases the magnetic flux.
True.
What does the negative sign in Faraday’s law indicate?
The negative sign indicates the direction of the induced EMF opposes the change in magnetic flux.
What is the effect of moving a magnet towards a coil?
Moving a magnet towards a coil induces an EMF and current in the coil.
Fill in the blank: The phenomenon of inducing current in a coil by changing the current in another coil is called __________.
Mutual induction.
What is self-induction?
Self-induction is the phenomenon where a changing current in a coil induces an EMF in the same coil.
What is the relationship between induced EMF and the number of turns in a coil?
The induced EMF is directly proportional to the number of turns in the coil.
What happens to the induced current when the magnetic field is removed?
The induced current ceases when the magnetic field is removed.
What is the principle of a generator based on?
The principle of a generator is based on electromagnetic induction.
True or False: A changing electric field can also produce a magnetic field.
True.
What is the term for the opposition to the change in current in an inductor?
Inductive reactance.
Fill in the blank: The device that converts mechanical energy into electrical energy is called a __________.
Generator.
What is the role of a transformer?
A transformer changes the voltage of alternating current using the principle of electromagnetic induction.
What is the effect of increasing the speed of a coil moving in a magnetic field?
Increasing the speed of the coil increases the induced EMF.
What does the term ‘eddy currents’ refer to?
Eddy currents are loops of electric current induced within conductors by a changing magnetic field.
True or False: Eddy currents can cause heating in materials.
True.
What is the formula for magnetic flux (Φ)?
Φ = B × A × cos(θ), where B is the magnetic field, A is the area, and θ is the angle between the field and the normal to the surface.
What practical applications utilize electromagnetic induction?
Applications include electric generators, transformers, inductors, and magnetic levitation.
Fill in the blank: The induced EMF can be increased by increasing the __________ of the magnetic field.
Strength.
What is alternating current (AC)?
Alternating current (AC) is an electric current that reverses direction periodically.
True or False: AC flows in only one direction.
False
Fill in the blank: The frequency of AC is measured in _____.
Hertz (Hz)
What is the standard frequency of AC in most of North America?
60 Hz
What is the standard frequency of AC in most of Europe?
50 Hz
Define the term ‘phase’ in the context of alternating current.
Phase refers to the position of a point in time on a waveform cycle of AC.
What is the peak voltage in an AC system?
The peak voltage is the maximum voltage reached during one cycle of the AC waveform.
True or False: AC voltage can be transformed to higher or lower levels using transformers.
True
What device is commonly used to convert AC to DC?
A rectifier
What is the root mean square (RMS) value of an AC voltage?
The RMS value is a mathematical measure of the effective voltage or current of an AC waveform.
Multiple Choice: Which waveform is commonly associated with AC?
Sine Wave
What is the main advantage of using AC over DC for power transmission?
AC can be easily transformed to higher voltages for efficient long-distance transmission.
Fill in the blank: In an AC circuit, the _____ indicates the phase difference between voltage and current.
power factor
What are the two main types of AC generators?
Synchronous and asynchronous generators.
True or False: AC is used exclusively for residential and commercial power supply.
False
What is the significance of the 60 Hz frequency in AC systems?
It is the frequency at which most electrical devices are designed to operate in North America.
What is a disadvantage of using AC?
AC can cause more losses in resistive materials compared to DC.
Multiple Choice: Which of the following is a common application of AC?
Powering household appliances
What is the role of capacitors in AC circuits?
Capacitors store and release electrical energy, affecting the phase and power factor.
Fill in the blank: The _____ is the time taken to complete one full cycle of an AC waveform.
period
What is the relationship between frequency and period in AC?
Frequency is the reciprocal of the period (Frequency = 1/Period).
True or False: In a single-phase AC system, there is only one alternating voltage.
True
What is three-phase AC?
Three-phase AC is a type of power generation, transmission, and distribution that uses three alternating currents, each phase 120 degrees apart.
Fill in the blank: The term ‘inductive reactance’ refers to the opposition to the flow of current caused by _____ in an AC circuit.
inductors
What is the purpose of an inverter in electrical systems?
An inverter converts DC electricity into AC electricity.
