OCR B Physics Chapter 3 – Electric Circuits

Match the following circuit components

• Resistor

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• Lamp

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• Diode

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• LDR

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Diane investigates how the resistance of a wire changes with the length of wire.

She uses this circuit on the image.

Diane said "I expected resistance to be proportional to length of wire. My graph does not show this. I noticed the wire got hot when it was short." Discuss Diane's comments and explain the shape of her graph. [6 marks]

This question is about the magnetic effect of an electric current.

Which one of the diagrams correctly shows the magnetic field caused by a wire conducting an electric current (electric current going into the paper)?

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Jasmine measured how the potential difference changed with the current in a wire. The graph shows the pattern of her results. Put ticks in the boxes next to the two correct conclusions from the graph. [2 marks]

• The wire has no resistance

• The resistance increases with current

• The resistance increases with the potential difference

• The resistance is fixed

• The wire is a linear part of the circuit

What is an electric current and what causes the electric current in a wire? [3 marks]

A pump is connected to the mains at 230 V and uses a current of 3 A.

Calculate the power of the pump. [3 marks]

Sam is doing an experiment to investigate the output of a solar panel. She is using a small photocell to model the panel.

She is measuring the power output of the photocell when it is different distances from a lamp.

At a distance of 25 cm, the power was 72 mW. The voltage across the photocell was recorded as 12 V. Using the equation:

power = potential difference × current

Calculate the current through the photocell. [4 marks]

Which statement about parallel circuits is correct?

• The current flowing through each loop is always the same

• The potential difference across each loop is always the same

• The resistance of each loop is always the same

What is the unit of electrical charge?

• Volt

• Ampere

• Coulomb

What is another term for potential difference?

• Current

• Voltage

• Resistance