Topic 2 - Electricity - 2.1 Current, Potential Difference and Resistance

Question 1

Draw the circuit symbol for a cell.

Answer 1

Question 2

Draw the circuit symbol for a battery.

Answer 2

Question 3

Draw the circuit symbol for a lamp.

Answer 3

Question 4

Draw the circuit symbol for a fuse.

Answer 4

Question 5

Draw the circuit symbol for a voltmeter.

Answer 5

Question 6

Draw the circuit symbol for an ammeter.

Answer 6

Question 7

Draw the circuit symbol for a diode.

Answer 7

Question 8

Draw the circuit symbol for a resistor.

Answer 8

Question 9

Draw the circuit symbol for a thermistor.

Answer 9

Question 10

Draw the circuit symbol for a variable
resistor.

Answer 10

Question 11

Draw the circuit symbol for an LDR.

Answer 11

Question 12

Draw the circuit symbol for an LED.

Answer 12

Question 13

What is electric current?

Answer 13

The flow of electrical charge.

Question 14

State the equation linking charge, current
and time. Give the units for the quantities
involved.

Answer 14

Q = I t
Charge (Coulombs), Current (Amperes),
Time (Seconds)

Question 15

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

Answer 15

Current is the same at all points in a
closed loop.

Question 16

What two factors does the current in a
circuit depend on?

Answer 16

1. Potential Difference (V)
2. Resistance (R)

Question 17

What equation should be used to
calculate potential difference if current
and resistance are known? State the
units for all 3 quantities.

Answer 17

V = I R
Potential Difference (V), Current (A),
Resistance (Ω)

Question 18

What is an ‘Ohmic Conductor’? State the
condition required.

Answer 18

●A conductor for which current and potential
difference are directly proportional
●Resistance remains constant as current
changes
●Temperature must be constant

Question 19

List four components for which
resistance is not constant as current
changes.

Answer 19

1. Lamps
2. Diodes
3. Thermistors
4. Light Dependant Resistors (LDRs)

Question 20

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

Answer 20

●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 21

What is different about current flow
through a diode?

Answer 21

●The current only flows in one direction
●Resistance is very high in the other
direction, preventing current flow

Question 22

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

Answer 22

The thermistor’s resistance decreases.

Question 23

Give two examples of when a thermistor
may be used.

Answer 23

1. In a thermostat to turn a heater on
   below a certain temperature
2. In a freezer to turn on a cooler when
   the temperature becomes too high

Question 24

State what happens to the resistance of
a LDR as light intensity decreases.

Answer 24

The LDR’s resistance increases.

Question 25

Give an application for a LDR.

Answer 25

●Street lights often use LDRs
●When light levels become too low, the
light gains sufficient current to turn on