Voltage

Question 1

How do electrons deliver energy around a circuit?

Answer 1

• When a component is connected to a battery in a circuit, electrons deliver energy from the battery.
• Each electron moves around the circuit and takes a fixed amount of energy from the battery as it passes through it.
• Electrons then deliver electricity to the bulb as they pass through it.
• After delivering energy to the component, each electron re enters the battery via the positive terminal to be re-supplied with more energy to deliver to the component

Question 2

What is the potential difference defined as?

Answer 2

Work done ( energy converted ) per unit charge moved, unit: volt, v.

Question 3

What is the formula for voltage?

Answer 3

V = W/Q
W = Work done ( joules, j ) 
Q = charge, C

Question 4

What is the formula for energy transfer when a charge passes through a component?

Answer 4

W = Q x V 
W = work done, joules, J
Q = charge, C
V = potential difference/voltage, Volts, v

Question 5

How can you measure the potential difference across a component?

Answer 5

Potential difference can be measured across a component by using a volt meter

Question 6

How should a voltmeter be connected in a circuit?

Answer 6

Potential difference across components in parallel is the same, therefore the voltmeter should be connected in parallel.

Question 7

What is the emf of a source defined as?

Answer 7

Electrical energy produced per unit charge passing through the source.
Unit: Volt, v

Question 8

What occurs when an electric current passes through a component with resistance?

Answer 8

Has a heating & magnetic effect.

Question 9

Why does a heating effect occur?

Answer 9

• In a device that has resistance , the work done on the device is transferred as thermal energy.
• Occurs because the charge carriers repeatedly collide with atoms in the device and transfer energy to them, results in the atoms vibrating more, leading to the resistor becoming hotter.

Question 10

How is the magnetic effect present in a spinning motor?

Answer 10

• In a motor turning at a constant speed, the work done on the motor is equal to the energy transferred to the load and surroundings by the motor.
• The kinetic energy of the motor thus remains constant.
• Charge carriers are electrons that need to be forced through the wires of the spinning motor coil against the opposing force on the electrons due to the motor’s magnetic field.

Question 11

What is the work done in a loudspeaker?

Answer 11

• Work done on the loudspeaker is transferred as sound energy.
• Electrons need to be forced through the wires of the vibrating loudspeaker coil against the force on them due to the loudspeaker magnet.

Question 12

What is the formula for work done by charge carriers?

Answer 12

W = I x V x Δt
V = Voltage
I = Current
W = Work done 
t = time

Question 13

What is the formula for energy transfer in the component?

Answer 13

Power = energy/time
(I x V x Δt) / Δt = IV
Power = I x V