Electric current

Question 1

Define electric current

Answer 1

Rate of flow of charge

Question 2

Define conventional current

Answer 2

From positive to negative

Question 3

Define electron flow

Answer 3

From negative to positive

Question 4

What is the formula for current, using current in coulombs and time?

Answer 4

I = Q/t
Current (A) = Current (C) / Time (s)

Question 5

Define potential difference

Answer 5

Voltage
The energy used up

Question 6

Define EMF

Answer 6

Electro-motive force
The energy supplied

Question 7

What is the formula for voltage, using work and charge?

Answer 7

V = W/Q
Potential difference = Work (J) / Charge (C)

Question 8

What is the formula for resistance, using voltage and current?

Answer 8

R = V/I
Resistance = Voltage (V) / Current (A)

Question 9

What are the 3 factors affecting resistance?

Answer 9

Thickness of wire
Length of wire
Temperature

Question 10

Define cell

Answer 10

DC only
Can run out (temporary)

Question 11

Define power supply

Answer 11

DC / AC
Not a cell
Doesn’t run out (permanent)

Question 12

Define variable resistor

Answer 12

Has the ability to change its resistance

Question 13

Define thermistor

Answer 13

Reacts to temperature - Changes its resistance according to temperature

Question 14

Define light-dependant resistor

Answer 14

Day-night switch. Relies on light to change its resistance

Question 15

Define diode

Answer 15

Changes AC current to DC current

Question 16

Define fuse

Answer 16

To stop current from going into the circuit that causes damage

Question 17

Describe a series circuit

Answer 17

Current has only 1 path
Voltage must add up to total EMF
Total Resistance = R1 + R2 + …
Current stays the same at all points in a circuit

Question 18

Describe a parallel circuit

Answer 18

Current has more than 1 path
Voltage is the same in the branches
The current adds up in the branches i.e. Total current = A1 + A2 + …
Total Resistance = 1/R1 + 1/R2 + …