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P3 ISA practice 2 – Student practical sheet
Investigating power loss in transformers
Aim
You are going to investigate your hypothesis into power loss in transformers
Equipment
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12 V ac power pack
2 voltmeters (ac)
2 ammeters (ac)
12 V bulb and holder
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connecting wires
2 pieces of single core thin wire
transformer/iron core or 6 inch nail
Safety
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Do not confuse the primary coil with 30 turns with the secondary coil with 15 turns.
What you need to do
1
Wrap the wire thirty times round the left hand arm of the core. If using a nail then wrap around
the left hand end of the nail.
2
Connect one end of this wire to one of the yellow terminals of the power pack, connect the
other to the negative or black terminal of the ammeter.
3
Connect the red or positive terminal of the ammeter to the other yellow terminal of the power
pack.
4
Connect the voltmeter across the yellow terminals of the power pack.
5
Wrap a second piece of wire around the right hand arm of the core. (If using a nail then wrap
around the right hand end of the nail.)
6
Connect one end of this wire to the negative or black terminal of the ammeter.
7
Connect the other end to one terminal of the bulb holder.
8
Connect the other terminal of the bulb holder to the red or positive terminal of the ammeter.
9
Connect the voltmeter across the bulb holder
10 Turn the power pack to 2 V ac setting and switch it on. The bulb is unlikely to light up but the
meters should have readings on them.
11 Record the readings on the voltmeter and ammeter connected to the power pack.
12 Record the readings on the voltmeter and ammeter connected to the bulb holder.
13 Turn off the power pack.
14 Reset the power pack to 4v and repeat steps 10-12.
15 Calculate the power at the primary (power pack side) and secondary (bulb holder side) coils
16 Repeat using 6V, 8V, 10V and 12V.
Sheet 1 of 2
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Primary side
voltmeter/V
Primary side
current
reading /A
Secondary
side
voltmeter
reading/V
Secondary
side current
reading/A
Calculate the percentage loss of power using this formula: secondary power in watts x 100
primary power in watts
Calculate the secondary power by multiplying secondary voltage and current together.
Calculate the primary power by multiplying primary voltage and current together.
Calculations
12
10
8
6
4
2
Power pack setting/V
Meter readings
Primary
power/W
Secondary
power/W
Percentage
loss of power
P3 ISA practice 2 – Student practical sheet
Results chart – Investigating power loss in transformers
© Pearson Education Ltd 2011. Copying permitted for purchasing institution only. This material is not copyright free.
Sheet 2 of 2