Current of electricity

Question 1

Define

current

Answer 1

The rate of flow of electric charge past a point

Question 2

Define

charge and the coloumb

Answer 2

charge = current x time

Q = It

One coloumb is the charge which flows past a point in a circuit in a time of 1s when the current is 1A

Question 3

Define

potential difference

Answer 3

The energy converted from electrical energy to other forms of energy per unit charge, i.e. the work done by unit charge as it moves between two points.

V = W/Q

Question 4

Define

electromotive force (e.m.f.)

Answer 4

The energy converted from chemical to electrical energy per unit charge, i.e. the total work done when unit charge goes around a complete circuit.

E = W/Q

Question 5

Define

resistance and the ohm

Answer 5

The resistance of a component is the ratio of the potential difference across it to the current flowing through it.

R = V/I

The ohm is the resistance of a component when a p.d. of 1V drives a current of 1A through it.

Question 6

How do you calculate the power in a circuit?

Answer 6

P = VI = IR² = V²/R