Electric Current and Power

Question 1

Current,I

Answer 1

The rate of flow of charge in a circuit and us measured in Amperes.

Question 2

Potential Difference, V

Answer 2

This is the work done (energy transferred) per unit charge passing through two points in a circuit.

Question 3

Electromotive Force (emf)

Answer 3

This is the work done (energy transferred) per unit charge to current as it passes through a power supply (cell,PSU it battery)

Question 4

Resistance, R

Answer 4

This is defined as the ratio of the potential difference to the current passing through a conductor

Question 5

Ohms Law

Answer 5

The potential difference across a component is directly proportional to the current provided the temperature and other physical conditions remain constant

Question 6

Kirchhoff’s First Law

Answer 6

The total current entering any point in circuit must equal the total current leaving that point. Charge is conserved

Question 7

Kirchhoff’s Second Law

Answer 7

The sum of the p.d’s around a closed loop in the circuit is equal to the sum of the elf’s across the power supply. Energy is conserved

Question 8

Power,P

Answer 8

The rate of energy transfer per second. Measured in watts or joules per second

Question 9

Efficiency

Answer 9

The ratio of the useful energy transferred compared to the energy supplied. It has no units.

Question 10

Kilo-watt Hour (KWh)

Answer 10

A measure of the energy transferred in kw every hour

Question 11

Charge, Q

Answer 11

A fundamental property of matter and all charged objects experience the electrostatic force. Measured in coulombs, C