Current, Potential Difference and Resistance - Paper 1

Question 1

When will electrical charge flow through a closed circuit?

Answer 1

When the circuit contains a source of potential difference.

Question 2

Define electrical current

Answer 2

Electrical current is a flow of electrical charge. The size of the current is the rate of flow of charge.

Question 3

Describe ohmic conductors

Answer 3

The current through ohmic conductors (at a constant temperature) is directly proportional to the potential difference across the resistor.

Question 4

Describe the changing resistance and IV curve of a filament lamp.

Answer 4

The resistance of a filament lamp increases as the temperature of the filament increases.
Current increases with potential difference at a rate that decreases as the size of the potential difference increases.

Question 5

Describe the changing resistance and IV curve of a diode.

Answer 5

The current through a diode flows in one direction only. The diode has a very high resistance in the reverse direction.
Current is 0 until it increases with potential difference past a certain positive threshold.

Question 6

Describe the changing resistance and an application of a thermistor.

Answer 6

The resistance of a thermistor decreases as the temperature increases.
Thermistors can be used in thermostats.

Question 7

Describe the changing resistance and an application of an LDR.

Answer 7

The resistance of an LDR decreases as light intensity increases.
LDRs can be used to turn lights on when it gets too dark.