Paper One: Electric Circuits

Question 1

What is the equation for charge (in words) that relates Charge, Current and Time?

Answer 1

Charge = Current x Time ( Q = I x T ).

Electric current is the rate of flow of charged particles.

Question 2

What is the equation (in words) for Voltage that relates Voltage, Work Done and Charge.

Answer 2

Voltage = Work Done / Charge

Potential difference is work done per unit charge.

Question 3

What is the equation relating Voltage, Current and Resistance.

Answer 3

Voltage = Current x Resistance ( V = I R ).

Question 4

The distribution of current in a circuit is a consequence of?

Answer 4

Charge Conservation.

Question 5

The distribution of potential difference in a circuit is a consequence of?

Answer 5

Energy Conservation.

Question 6

What is the equation for resistivity?

Answer 6

Resistance = Resistivity x Length / Area ( p L / A ).

Question 7

What is the meaning of each letter in the equation I = n q v a?

Answer 7

Current = (density of charge carriers) x (charge of one charge carrier) x (average speed of charge carriers) x (cross sectional area of wire).

Question 8

Define Electromotive Force.

Answer 8

When charge flows through a cell it is given energy by the cell.

The number of joules of energy given to each coulomb of charge that passes through the cell is the e.m.f. of the cell.

Question 9

Define Internal Resistance.

Answer 9

All materials have some resistance. Therefore, a cell must have resistance. This resistance is called the internal resistance of the cell.

Question 10

How do you combine resistors in parallel?

Answer 10

1/Rtotal = 1/R1 + 1/R2 + 1/R3

Question 11

How do you combine resistors in series?

Answer 11

Rtotal = R1 + R2 +R3