Potential Difference and Resistance

Question 1

True or false? For a given potential difference, the smaller the resistance of a component, the smaller the current through it will be.

Answer 1

False
Resistance is anything that slows down the flow of charge. So for a given potential difference, the smaller the resistance of a component, the greater the current through it will be.

Question 2

True or false? Work is done when charges flow in a circuit.

Answer 2

True

Charges in a circuit do work against resistance

Question 3

What equation links energy transferred, charge moved and potential difference?

Answer 3

Energy transferred = charge moved x potential difference or E = Q x V

Question 4

A current flows through a 20Ω component when a potential difference of 9V is placed across it. What is the size of the current?

Answer 4

0.45 A
V = I x R so I = V / R
9 / 20 = 0.45 A

Question 5

A charge of 2000C flows through a motor. The potential difference across the motor is 230V. How much energy is transferred by the motor?

Answer 5

460000J

E = Q x V = 2000 x 230 = 460000J ( =460kJ)

Question 6

When a current flows through a resistor, the resistor heats up. Explain why.

Answer 6

A resistor is made of lattice ions. When a current flows through the resistor, the electrons collide with these ions. This transfers energy to the kinetic energy stores of the ions, which cause them to vibrate more and so the temperature of the resistor increases.

Question 7

State and explain what happens to the resistance of a resistor as its temperature increases.

Answer 7

The resistance of the resistor increases, as its ions vibrate more, so there are more collisions between the ions and the electrons and it becomes harder for a current to flow.