Electrical working, ion lattice, heating and electrical safety

Question 1

Electric Current and Resistor Heating

Answer 1

When there is an electric current in a resistor, energy is transferred to heat the resistor.

Question 2

Energy Dissipation and Resistance

Answer 2

Electrical energy is dissipated as thermal energy in the surroundings when an electric current does work against electrical resistance.

Question 3

Energy Transfer in Resistors

Answer 3

The energy transfer in resistors is due to collisions between electrons and ions in the lattice, which causes the material to heat up.

Question 4

Reducing Unwanted Energy Transfer

Answer 4

Unwanted energy transfer can be reduced by using low-resistance wires, which minimize energy loss as heat.

Question 5

Heating Effect of Electric Current

Answer 5

Advantages:

Useful in heating devices like kettles,
toasters.

Disadvantages:

Can cause energy waste in unwanted areas, like wires in electronic devices.

Question 6

Equation for Energy Transfer

Answer 6

Equation:
Energy transferred (J) = Current (A) × Potential Difference (V) × Time (s)

Formula:
E = I × V × t

Question 7

Power and Energy

Answer 7

Power is the energy transferred per second and is measured in watts (W).

Question 8

Power Equation

Answer 8

Equation:
Power (W) = Energy transferred (J) ÷ Time taken (s)

Formula:
P = E ÷ t

Question 9

Power Transfer in Circuit Devices

Answer 9

Power transfer in any circuit device is related to the potential difference across it and the current passing through it.

Question 10

Electrical Power Equations

Answer 10

Equations:

Electrical power (W) = Current (A) × Potential Difference (V)
Formula: P = I × V

Electrical power (W) = Current² (A²) × Resistance (Ω)
Formula: P = I² × R

Question 11

Energy Transfer in Domestic Devices

Answer 11

In domestic devices, energy from batteries and a.c. mains is transferred to motors or heating elements (e.g., in microwaves or heaters).

Question 12

Direct vs Alternating Voltage

Answer 12

Direct voltage stays constant in one direction, while alternating voltage regularly reverses direction.

Question 13

Direct Current (D.C.)

Answer 13

Direct current (D.C.) is the movement of charge in one direction only. Cells and batteries supply D.C.

Question 14

Alternating Current (A.C.)

Answer 14

Alternating current (A.C.) is where the movement of charge changes direction periodically.

Question 15

UK Domestic A.C. Supply

Answer 15

UK Domestic A.C. Supply

Question 16

Live and Neutral Wires

Answer 16

Live wire: Carries the current to the appliance.
Neutral wire: Completes the circuit by carrying the current back.

Question 17

Earth Wire and Fuses

Answer 17

The earth wire provides a path for current to the ground in case of a fault. Fuses or circuit breakers protect circuits by disconnecting when current exceeds safe limits.

Question 18

Position of Switches and Fuses

Answer 18

Switches and fuses should be connected in the live wire to cut off the supply to the appliance completely.

Question 19

Mains Wire Potential Differences

Answer 19

Live wire: ~230 V
Neutral wire: ~0 V
Earth wire: 0 V (for safety)

Question 20

Dangers of Live to Earth Connection

Answer 20

Connecting the live wire to earth can cause a dangerous short circuit, leading to electric shocks or fire.

Question 21

Power Ratings and Energy Changes

Answer 21

The power ratings of domestic appliances reflect how much energy they transfer per second, such as heaters converting electrical energy into thermal energy.