Current of Electricity

Question 1

Define current

Answer 1

Electric current is defined as the rate of flow of charged particles.
I = Q/t
I = nAvq

Question 2

Define electric charge

Answer 2

The charge which flows past a point in time is the product of current and time, if the current is steady.

Question 3

Define potential difference

Answer 3

The potential difference across a device is the electrical energy converted to other forms of energy per unit charge passing through the device.
V = W/Q

Question 4

Define electromotive force

Answer 4

The electromotive force of a source is the electrical energy, converted from other forms of energy per unit charge, transferred by the source in driving unit charge round a complete circuit.

Question 5

Define power

Answer 5

Power is the rate at which work is done
P = VI = dW/dT

Question 6

Define resistance

Answer 6

Resistance of a conductor is defined as the ratio of the potential difference across the conductor to the current flowing through it.

Question 7

State Ohm’s law

Answer 7

The current I through a metallic conductor is proportional to the potential difference V across its ends under constant physical conditions.

Question 8

Define resistivity

Answer 8

Resistivity is a measure of how strongly a material opposes electric current. It characterises the resistance of materials at a fixed temperature regardless of the materials’ dimensions.
R = pl/A

Question 9

Formula for terminal pd of a cell

Answer 9

V = emf - Ir