2C2 Electricity and Magnetism

Question 1

What is electricity?

Answer 1

The presence and flow of electric charge.

It is usually carried by electrons moving through a conductor.

Question 2

What is electric charge?

Answer 2

A property that determines how matter interacts with electric and magnetic fields.

Charge exists in two forms: positive and negative. Objects with the same charge repel each other, while opposite charges attract.

Question 3

True or False:

Like charges attract each other.

Answer 3

False

Like charges repel each other, while opposite charges attract.

Question 4

What is the unit of electric charge?

Answer 4

Coulomb

(C)

One Coulomb is approximately equal to 6.242 × 10¹⁸ elementary charges.

Question 5

What does Coulomb’s law describe?

Answer 5

The force between two charges.

It states that the force is directly proportional to the product of the charges and inversely proportional to the square of the distance between them.

Question 6

What is the formula for Coulomb’s law?

Answer 6

F = k × (q₁ × q₂) / r²

Where:

F is the electrostatic force between the charges,
k is Coulomb’s constant,
q₁ and q₂ are the charges, and
r is the distance between them.

Question 7

Fill in the blank:

Opposite charges _______ each other.

Answer 7

attract

Opposite charges create an attractive force, as described by Coulomb’s law.

Question 8

What happens when charges are separated by a greater distance?

Answer 8

The force between them decreases.

According to Coulomb’s law, the force is inversely proportional to the square of the distance between the charges.

Question 9

Fill in the blank:

Coulomb’s constant, k, is approximately _______ N·m²/C².

Answer 9

8.99 × 10⁹

Coulomb’s constant is used to calculate the electrostatic force between two charges.

Question 10

What is an electric field?

Answer 10

A region around a charge where other charges experience a force.

The strength depends on the magnitude of the charge and the distance from it.

Question 11

True or False:

The electric field strength increases with distance from the charge.

Answer 11

False

The electric field strength decreases with the square of the distance from the charge.

Question 12

How is the strength of an electric field calculated?

Answer 12

E = F / q

Where E is the electric field, F is the force, and q is the charge.

Question 13

True or False:

The electric field lines point toward negative charges.

Answer 13

True

The field lines always point from positive to negative charges, indicating the direction of the force that would be exerted on a positive test charge.

Question 14

What is the unit of electric field strength?

Answer 14

N/C

(Newtons per Coulomb)

The unit describes the force exerted on a charge in an electric field.

Question 15

True or False:

The electric field strength is stronger the farther you are from the charge.

Answer 15

False

The electric field strength decreases with the square of the distance from the charge.

Question 16

What determines the direction of an electric field?

Answer 16

The sign of the charge.

Electric fields point away from positive charges and toward negative charges.

Question 17

What type of force does an electric field exert on a charge?

Answer 17

Attractive or repulsive force.

Positive charges are repelled by other positive charges and attracted to negative charges, and vice versa.

Question 18

What happens to the force between two charges when the distance is halved?

Answer 18

It quadruples.

According to Coulomb’s law, force is inversely proportional to the square of the distance, so halving the distance increases the force by a factor of four.

Question 19

True or False:

Electric fields can only exist around charged objects.

Answer 19

True

They are created by charges, and their presence can be detected by observing forces on other charges.

Question 20

What is a conductor?

Answer 20

A material that allows electric charge to flow easily.

Metals like copper and silver are good conductors due to the availability of free electrons.

Question 21

What is an insulator?

Answer 21

A material that resists the flow of electric charge.

Insulating materials, like rubber and glass, have tightly bound electrons that do not move freely.

Question 22

True or False:

Metals are good conductors of electricity.

Answer 22

True

Metals, especially copper and silver, have free electrons that allow them to conduct electricity efficiently.

Question 23

Fill in the blank:

Rubber is an example of a good _______.

Answer 23

insulator

Rubber is often used in electrical wires to prevent accidental electrical contact.

Question 24

What is the function of an insulator in electrical wiring?

Answer 24

To prevent the unwanted flow of electric charge.

Insulators are used to cover wires, ensuring that the current only flows through the designated path.

Question 25

What is the **electric field** inside a conductor?

Answer 25

Zero ## Footnote In a conductor in electrostatic equilibrium, charges move to the surface, and the electric field inside cancels out.

Question 26

# True or False: In conductors, free electrons move **towards** the positive end when a voltage is applied.

Answer 26

True ## Footnote Free electrons in conductors move toward the positive terminal, creating an electric current.

Question 27

What is **electric current**?

Answer 27

The **flow** of electric charge. ## Footnote Current is carried by electrons in a conductor.

Question 28

What is the **unit** of electric current?

Answer 28

Ampere | (A) ## Footnote One ampere is equal to one coulomb of charge passing through a conductor per second.

Question 29

# Fill in the blank: \_\_\_\_\_\_\_\_ is the **opposition** to the flow of electric current.

Answer 29

Resistance ## Footnote Resistance depends on the material, length, and cross-sectional area of the conductor.

Question 30

# True or False: An Ohm (Ω) is the **unit** of resistance.

Answer 30

True ## Footnote One ohm is the resistance that allows one ampere of current to flow when one volt is applied across the conductor.

Question 31

What is **voltage**?

Answer 31

The **difference** in electric potential between two points. ## Footnote Voltage is responsible for driving the current through a conductor and is measured in volts (V).

Question 32

What is the **unit** of voltage?

Answer 32

Volt | (V) ## Footnote One volt is the potential difference that will move one coulomb of charge when one joule of work is done.

Question 33

What is **Ohm’s law**?

Answer 33

The **relationship** between voltage, current, and resistance. ## Footnote Ohm's law is expressed as: **V = I × R**, where V is voltage (volts), I is current (amperes), and R is resistance (ohms).

Question 34

# True or False: **Power** in an electrical circuit is calculated by multiplying voltage by current.

Answer 34

True ## Footnote Power is given by **P = V × I**, where P is power (watts), V is voltage (volts), and I is current (amperes).

Question 35

What is the **formula** for Ohm's Law?

Answer 35

V=IR ## Footnote Where voltage (V) = current (I) multiplied by resistance (R).

Question 36

What is the **unit** of electrical power?

Answer 36

Watt | (W) ## Footnote One watt is equivalent to one joule of energy used per second.

Question 37

# True or False: Power is the **same** as energy.

Answer 37

False ## Footnote Power is the rate at which energy is used, while energy is the total work done over time.

Question 38

# Define: Direct current | (DC)

Answer 38

Electric current that flows in **one direction**. ## Footnote DC is commonly used in *batteries*, where electrons flow from the negative to the positive terminal.

Question 39

What is **alternating current**? | (AC)

Answer 39

Electric current that **changes direction**. ## Footnote AC is used in most *household* electrical systems, with current oscillating back and forth.

Question 40

# Fill in the blank: The formula for resistance is **R = V / I**, where V is the \_\_\_\_\_\_\_ and I is the current.

Answer 40

voltage ## Footnote This formula is *derived* from Ohm’s law and shows how resistance relates to voltage and current.

Question 41

What is **capacitance**?

Answer 41

The ability of a component to **store an electric charge**. ## Footnote Capacitance is measured in *farads (F)*, and capacitors are used to store and release electrical energy. It is calculated by dividing the charge stored on the capacitor by the voltage.

Question 42

What is the **unit** of capacitance?

Answer 42

Farad | (F) ## Footnote One farad is the capacitance of a capacitor that stores one coulomb of charge when one volt is applied.

Question 43

# True or False A capacitor is a **device** used to store electrical energy.

Answer 43

True ## Footnote Capacitors store charge between two conductors separated by a dielectric material.

Question 44

What is a **battery**?

Answer 44

A device that converts **chemical energy** into DC power. ## Footnote Batteries convert chemical energy into electrical energy and are commonly used in portable devices.

Question 45

What is a **generator**?

Answer 45

A device that converts **mechanical energy** into electrical energy. ## Footnote Generators produce alternating current (AC) by rotating a coil within a magnetic field.

Question 46

What is the function of a **photocell**?

Answer 46

To convert **light energy** into electrical energy. ## Footnote Photocells, or solar cells, are used in devices like solar panels to generate electricity from sunlight.

Question 47

What is a **series** circuit?

Answer 47

A **circuit** where components are connected end to end. ## Footnote The **current** is the same through all components, but the voltage is divided among them.

Question 48

What happens to the total **resistance** in a series circuit?

Answer 48

It increases. ## Footnote The a series circuit, the total resistance is the sum of the individual resistances: R_total = R₁ + R₂ + ...

Question 49

What is a **parallel circuit**?

Answer 49

A circuit where components are connected across **common** points. ## Footnote The voltage across all components is the same, but the current is divided among them.

Question 50

# Fill in the blank: In a **parallel** circuit, the total resistance \_\_\_\_\_\_\_\_.

Answer 50

decreases ## Footnote The total resistance is calculated using: 1/Rₜₒₜₐₗ = 1/R₁ + 1/R₂ + …, where R₁ and R₂ represent the resistance of each individual circuit.

Question 51

# True or False: In a parallel circuit, the current is the **same** through all components.

Answer 51

False ## Footnote The voltage is the same, but the current divides according to the resistance of each branch.

Question 52

What is the equivalent **resistance** of two resistors in parallel?

Answer 52

Rtotal = R₁ + R₂ / R₁ × R₂ ## Footnote This formula is used for *two resistors* in parallel to find the total resistance of the circuit.

Question 53

What happens if **more** resistors are added in parallel?

Answer 53

The total resistance **decreases**. ## Footnote Adding resistors in parallel provides more paths for the current, reducing the overall resistance.

Question 54

What happens to the **current** if more resistors are added in series?

Answer 54

It decreases. ## Footnote Adding resistors increases the total resistance, which *reduces* the overall current according to Ohm's law.

Question 55

What does a **fuse** do in a circuit?

Answer 55

It **protects** the circuit from excessive current. ## Footnote A fuse **melts** if the current exceeds a certain limit, preventing damage to the components.

Question 56

# True or False: The voltage across all components in a series circuit is the **same**.

Answer 56

False ## Footnote In a series circuit, the voltage is divided among the components according to their resistances.

Question 57

# True or False: The total resistance in a parallel circuit is **greater** than the resistance of the smallest resistor.

Answer 57

False ## Footnote The total resistance in a parallel circuit is **always** less than the resistance of the smallest individual resistor.

Question 58

# Define: magnetic forces

Answer 58

A force that results from the **attraction or repulsion** between electrically charged particles in motion.

Question 59

What are the two **types** of magnetic poles?

Answer 59

North and South ## Footnote Opposite poles attract each other, while like poles repel.

Question 60

# Fill in the blank: The **region** around a magnet where magnetic forces are exerted is called a/an \_\_\_\_\_\_\_ \_\_\_\_\_.

Answer 60

magnetic field ## Footnote They are represented by field lines that emerge from the north pole and enter the south pole.

Question 61

# True or False: Magnetic poles can exist **independently**.

Answer 61

False ## Footnote Magnetic poles always come in pairs; cutting a magnet results in two smaller magnets, each with a north and south pole.

Question 62

What **happens** when you bring the north pole of one magnet close to the north pole of another magnet?

Answer 62

They **repel** each other. ## Footnote This demonstrates the principle that like poles repel.

Question 63

What **shape** do magnetic field lines around a bar magnet take?

Answer 63

Closed loops ## Footnote These lines emerge from the north pole, curve around, and re-enter at the south pole.

Question 64

What is a **permanent magnet**?

Answer 64

A magnet that **remains** magnetized without external power. ## Footnote Examples include bar magnets and horseshoe magnets.

Question 65

What is an **electromagnet**?

Answer 65

A magnet formed by electric current through a **coil**. ## Footnote Electromagnets can be turned on or off by *controlling* the electric current.

Question 66

# True or False: Electromagnets are **weaker** than permanent magnets.

Answer 66

False ## Footnote Electromagnets can be made much stronger by increasing the current or the number of coils.

Question 67

# Fill in the blank: The **core** of an electromagnet is typically made of \_\_\_\_\_\_\_.

Answer 67

iron ## Footnote Iron enhances the magnetic field produced by the current in the coil.

Question 68

What **advantage** do electromagnets have over permanent magnets?

Answer 68

Their magnetic field can be **controlled** ## Footnote They can be turned on and off, as well as adjusted, making them useful in devices such as electric motors and relays.

Question 69

How is the direction of the magnetic field around a current-carrying wire **determined**?

Answer 69

By **using** the right-hand rule. ## Footnote Point your thumb in the direction of current flow; your curled fingers show the direction of the magnetic field.

Question 70

# True or False: A straight current-carrying wire **produces** a circular magnetic field.

Answer 70

True ## Footnote The magnetic field forms concentric circles around the wire.

Question 71

# Fill in the blank: The **strength** of the magnetic field around a current-carrying wire is _______ proportional to the distance from the wire.

Answer 71

inversely ## Footnote This means the field gets weaker as you move farther away.

Question 72

What is **electromagnetic induction**?

Answer 72

The process of generating an electric current by **changing** a magnetic field. ## Footnote This principle was discovered by Michael Faraday.

Question 73

# True or False: A **stationary** magnet near a stationary coil will generate an electric current.

Answer 73

False ## Footnote A changing magnetic field is necessary to induce a current.

Question 74

# Fill in the blank: The **device** used to demonstrate electromagnetic induction is called a/an \_\_\_\_\_\_\_.

Answer 74

generator ## Footnote Generators convert mechanical energy into electrical energy.

Question 75

What **law** quantitatively describes electromagnetic induction?

Answer 75

Faraday’s Law of Induction ## Footnote The law states that the induced voltage is proportional to the rate of change of the magnetic flux.

Question 76

What is the basic function of an **electric motor**?

Answer 76

To **convert** electrical energy into mechanical energy. ## Footnote This is achieved through the **interaction** of magnetic fields and current-carrying wires.

Question 77

What is the basic function of an **electric generator**?

Answer 77

To **convert** mechanical energy into electrical energy. ## Footnote This process relies on *electromagnetic induction*.

Question 78

# True or False: Both motors and generators **rely** on magnetic fields.

Answer 78

True ## Footnote Magnetic fields are essential for the operation of both devices.

Question 79

# Fill in the blank: The **rotation** of a coil in a magnetic field generates a \_\_\_\_\_\_\_.

Answer 79

current ## Footnote This is the principle behind how generators work.

Question 80

What **component** of a motor ensures continuous rotation in the same direction?

Answer 80

The commutator. ## Footnote The commutator *reverses* the current direction in the coil, maintaining consistent torque.

Question 81

What is the role of the **armature** in a motor?

Answer 81

To **carry the current** and rotate within the magnetic field. ## Footnote The armature is the *moving part* of a DC motor.

Question 82

What is the function of a **stator** in a motor?

Answer 82

To provide a **stationary** magnetic field. ## Footnote The rotor moves within this field to create motion.

Question 83

# Fill in the blank: A generator's **rotor** \_\_\_\_\_\_\_ to induce current in the stator.

Answer 83

rotates ## Footnote The rotor is the moving part in an AC motor, while the stator remains stationary.