Student worksheet ( 1 of 3 )
Hot wires
It’s not just the atmosphere at a music concert that’s electric! Think
of all the lights, instruments and sound systems that need electricity
to work.
Electrical engineers help to design, build and test electricallypowered products and circuits. At a music concert, they make sure
all the electrical equipment is set up properly. It has to work and
be safe.
Electrical power can be dangerous – it must be controlled carefully
to avoid electric shocks, damaged equipment and even fires.
Imagine you’re an electrical engineer. Your favourite band is
coming to town. You’ve been asked to check that all their
electrical equipment will be safe using the venue’s power supply.
You need to understand how to control electricity and protect
electric circuits.
Your task
You’re going to investigate how a fuse protects equipment
in an electrical circuit.
Read the instructions carefully before beginning.
What you will need
• DC power supply
• lamp (light bulb in holder)
• ammeter (0 to 1 A)
• 4 x connecting wires
• 2 x crocodile clips
• Blu-tack
• 2 x pieces of aluminium foil (1 cm by 2 cm)
• fine grade steel wool (approximately 7 cm single strand) –
to act as fuse wire
• heat-resistant mat
• eye protection
Safety
Take care – the steel wool will get extremely hot during the
experiment. Wear eye protection.
www.tomorrowsengineers.org.uk
Electr
ical en
gineers
equipm
make s
ent is s
ure
afe.
Student worksheet ( 2 of 3 )
What you need to do
1. Make sure the power supply is turned off.
dc power supply
+
–
2. Use the components to build a simple circuit
with the lamp and ammeter in series. Make
sure you connect the ammeter correctly
(ammeter + to power supply +).
fuse wire
A
3. Leave a gap in your circuit. For example, do not attach one of the wires to the lamp holder.
lamp
4. Carefully place one end of the steel wool on
a piece of aluminium foil, and stick it down
with Blu-tack. Stick the other end onto the
second piece of foil. The strand of steel wool
will act as your fuse wire.
5. Place your fuse assembly on a heat-resistant
mat. Connect it across the gap in your circuit
by attaching crocodile clips to the foil.
6. Ask your teacher to check your circuit.
aluminium foil
Blu-tack
crocodile clip
fuse wire
(7 cm strand of steel wool)
heat-resistant mat
7. S et the power supply to its lowest setting (1 or
1.5 V) and turn it on. Record the voltage.
8. Read the ammeter and record the current. Also record any observations about the light bulb and
fuse wire.
9. Increase the voltage of the power supply by 1 or 1.5 V.
10.Record the new voltage, current and any observations.
11. Repeat steps 9 and 10 until the steel wool fuse ‘blows’. (Warning: Fuse wire will get VERY HOT).
12.Return the power supply to its lowest setting and complete the circuit without the steel wool fuse,
to check that the light bulb is still working.
Results
1. Record your observations in a table like this:
power supply (V)
current (A)
any observations
light bulb
2. Draw a graph to show the relationship between voltage and current.
www.tomorrowsengineers.org.uk
fuse
Student worksheet ( 3 of 3 )
Questions
• What happens to the steel wool fuse when it ‘blows’?
• How else can you tell when the steel wool has blown?
• Describe what happened during your experiment.
• How do you explain the changes that you observed?
• What would have happened if there were no fuse in the circuit?
• Share your results with the rest of the class. How do they compare?
• Suggest why the results varied from one group to another.
• How could you improve your experiment?
• Suggest some further investigations you could carry out.
Extension
Use secondary sources (books and Internet) to find out about circuit breakers:
• How are they different from fuses?
• What is an electromagnet?
Engineers
• There are four engineers shown on the poster. What other engineers
do you think might be needed to help put on a live music performance?
• As well as working at music concerts, where else might you find an
electrical engineer? Try to think of at least three areas of work.
Belal Habib,
Packaging Engineer
www.tomorrowsengineers.org.uk