HELP

1 a Match the beginning of each sentence with the correct ending. Write out each complete sentence.

Beginning / Ending
A The voltage measured across a cell / 1 shows that energy is being transferred out of a circuit.
B The voltage measured across a bulb / 2 shows that more energy is being transferred into the circuit by two cells.
C No voltage can be measured across the wires in a circuit which / 3 shows that energy is being transferred into a circuit.
D The voltage measured across two identical connected cells is larger than the voltage across only one cell which / 4 shows that no energy is being transferred in the wires.

b The objects in the boxes can all be found in electrical circuits.

Copy the headings below to make a table. Write each object into the correct column to show how each object transfers energy in a circuit.

Transfers energy into the circuit / Transfers energy out of the circuit

CORE

2 Look at the circuit diagrams. They have been set up to measure:

A the voltage across the bulb. C the voltage across the connecting wires.

B the voltage across the cell. D the voltage across the bulb.

There is a problem with each one. Explain what the problem is.

3 Look at the circuit diagrams below. The bulbs in each circuit are identical. The 1.5 V cells are also identical.

a What is the voltage across

i cell A? ii cell B? iii cell C?

b Which bulb transfers the most energy out of the circuit?

c Which bulb will be the least bright?

d All three circuits are switched on and left. Which circuit will transfer all the available energy out through the bulb first?

EXTENSION

4 Jim wants to use a solar cell to power the fan on his desk in the summer. He sets up a circuit containing the solar cell, a fan and connecting wires. He wants to find out if all the energy from the solar cell is being converted into movement of his fan.

a How would Jim connect a voltmeter to measure:

i the voltage transferred into the circuit?

ii the voltage transferred out of the circuit?

b Jim works out the amount of kinetic energy transferred into the fan. It is less than the energy transferred into the circuit.

Explain what has happened to the rest of the energy.

c Jim swaps his fan for one with a much heavier fan blade.

i How will this affect the speed of the fan?

ii Explain why changing the fan will have this effect.

iii What must Jim do to make the larger fan run at the same speed as the smaller one?

© Harcourt Education Ltd 2004 Catalyst 3

This worksheet may have been altered from the original on the CD-ROM.