Resistance

Question 1

How does resistance affect current in a

circuit?

Answer 1

As the total resistance of a circuit
increases, the current flowing through the
circuit decreases.

Question 2

How can the current in a circuit be varied?

Answer 2

Using a variable resistor.

Question 3

Give the equation linking current with resistance

Answer 3

p.d. (V) = current (A) x resistance (Ω)

V = IR

Question 4

How is total resistance affected by two resistors in series?

Answer 4

The total resistance increases; it is equal to the sum of the two resistors.

Question 5

How is total resistance affected by two resistors in

parallel?

Answer 5

The total resistance decreases; it is less
than the resistance of the resistor with
the lowest resistance.

Question 6

What is an ‘Ohmic Conductor’? State the condition

required

Answer 6

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

Question 7

List four components for which resistance is not

constant as current changes

Answer 7

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

Question 8

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

Answer 8

● Resistance increases
● Metal ions have more kinetic energy, so vibrate more, colliding more frequently with electrons as they flow through the metal
● This creates more resistance to current flow

Question 9

What is different about current flow

through a diode?

Answer 9

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

Question 10

State what happens to the resistance of a thermistor

as temperature increases

Answer 10

The thermistor’s resistance decreases

Question 11

Give two examples of when a thermistor may be

used

Answer 11

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 12

State what happens to the resistance of an LDR as

light intensity decreases

Answer 12

The LDR’s resistance increases

Question 13

Give an application for a LDR

Answer 13

● Street lamps or night lights
● When light levels drop (at night),
resistance increases and the light
gains sufficient current to turn on

Question 14

How do diodes work?

Answer 14

A diode only allows current to flow in one direction. If current is flowing the right way, the resistance is large for small voltages (up until about 0.6V), but then at higher voltages becomes very small.

Question 15

What electrical component does this
graph represent?

https://pmt.physicsandmathstutor.com/download/Physics/GCSE/Notes/Edexcel/10-Electricity-and-Circuits/Flashcards/Flashcards%20-%20Topic%2010%20Resistance%20-%20Edexcel%20Physics%20GCSE.pdf

Answer 15

Diode