2.1: Current, PD, and Voltage

Question 1

What is electrical current?

Answer 1

Flow of electrical charge

Question 2

PEVEQ

Answer 2

P = I * V
E = P * T
V = I * R
E = V * Q
Q = I * T
P = I2 * R

Question 3

What can be said about the value of current at any point in a single closed loop?

Answer 3

Current is the same at all points in a closed loop

Question 4

What 2 factors does current in a circuit depend on?

Answer 4

• resistance

- voltage/potential difference

Question 5

What is an ‘ohmic conductor’?

State the condition required.

Answer 5

• A conductor for which current and PD are directly proportional
• Resistance remains constant as current changes
• Temperature must be constant

Question 6

List 4 components for which resistance is not constant as current changes

Answer 6

• lamps
• diodes
• thermistors
• light dependant resistors (LDRs)

Question 7

What happens to the resistance of a filament lamp as the temperature increases?
Why?

Answer 7

• resistance increases
• ions in metal have more energy, so vibrate more, causing more collisions with electrons as they flow through the metal, creating greater resistance to current flow

Question 8

What is different about current flow through a diode?

Answer 8

• current only flows in one direction

- resistance is very high in the other direction, preventing current flow in that direction

Question 9

State what happens to the resistance of a thermistor as temperature increases

Answer 9

thermistor’s resistance decreases

Question 10

Give 2 examples of when a thermister might be used

Answer 10

• in a thermostat to turn the heater on below a certain temperature
• in a freezer to turn on a cooler when the temperature becomes too high