csec physics pd lab - factors affecting strength of electromagnet
TRANSCRIPT
Title: Electromagnetism
Hypothesis: The 4 factors which can affect the strength of an electromagnet are the type of
core used, the number of turns of wire, the magnitude of the current used and
the shape of the solenoid.
Aim: To investigate the factors which affect the strength of an electromagnet.
Apparatus: iron nail, horse-shoe nail, copper rod, nickel rod, 100cm length of insulated wire,
connecting wires, 12V power supply, ammeter, rheostat, switch, electronic
balance, iron filings, brush, petri-dishes
Procedure:
1. The circuit was set up as shown above, with the connecting wires wound 50 times
around the iron nail.
2. The switch was turned on. The rheostat was adjusted and the ammeter checked to
ensure that 5 amps of current were flowing through the circuit.
3. The stopwatch was started and the nail placed inside of the petri-dish with the iron
filings. After 30 seconds the switch was turned off and the stopwatch was stopped.
4. A second petri-dish was weighed on the electronic balance and its mass was recorded as
mi.
5. The nail was taken out from the iron filings and placed over the second petri -dish,
allowing the iron filings to fall onto it. A brush was used to brush off any remaining
filings still on the nail.
6. The initial mass of the dish was subtracted from the new mass of the dish mf to obtain
the mass of the iron filings.
7. Steps 2-6 were repeated and an average of the mass of iron filings picked up was
calculated.
8. Steps 2-7 were repeated using a nickel then a copper rod.
9. Keeping all other factors constant, steps 2-7 were repeated using 10 turns around the
iron nail and increasing the no. of turns each time by ten, stopping at 60 turns.
10. Keeping all other factors constant, steps 2-7 were repeated but instead of using 5 amps,
the rheostat was used to adjust the current to 1 amp. The current was increased by 1
amp each time up until 5 amps.
11. Keeping all other factors constant, steps 2-7 were repeated using the iron nail, then
using the horse-shoe nail.
Results:
A. Below: Table 1 showing effect of type of core used
Types of Core Mass Force 1 2 Average
Iron 27 26 26.5 0.265
Nickel 25 25 25.0 0.250 Copper 24 25 24.5 0.245
Shape – rod Variables
Number of Turns – 50 Manipulated – Type of Core
Current – 5A Responding – Mass of Filings
B. Below: Table 2 showing effect of no. of turns
No. of Turns Mass Force
1 2 Average
10 5.0 5.0 5.00 0.500
20 12 9.0 10.5 0.105
30 15 16 15.5 0.155
40 21 19 20.0 0.200 50 26 27 26.5 0.265
60 32 32 32.0 0.320 Type of Core – Iron Variables
Current – 5A Manipulated – No. of Turns
Shape – rod Responding – Mass of Filings
C. Table 3 showing effect of current
Current Mass Force
1 2 Average
1 5.0 5.0 5.00 0.500 2 10 11 10.5 0.105
3 14 16 15.0 0.150 4 21 22 21.5 0.215
5 27 26 26.5 0.265
Shape – rod Variables
Manipulated – Current Number of Turns – 50
Type of Core – Iron Responding – Mass of Filings
D. Table 4 showing effect of shape of an electromagnet
Shape Mass Force 1 2 Average
Rod 26 27 26.5 0.265
Horse-Shoe 27 27 27.0 0.270 Type of Core – Iron Variables
Number of Turns – 50 Manipulated – Shape
Current – 5A Responding – Mass of Filings
Discussion:
An electromagnet is a magnet consisting essentially of a coil of insulated wire wrapped
around a soft iron core that is magnetized only when current flows through the wire.
The type of core used affected the strength of the electromagnet. Based on the results,
iron was shown to be the core which produced the strongest magnetic force, whilst copper
exhibited the least strength.
The results also showed that as the number of turns of coil increased, the strength of
the magnetic force increased. This is because when an solenoid has more turns of wire per unit
length, more fields line up and complement each other, thus producing a larger magnetic
effect. Furthermore, it was shown that increasing current increases the strength of the force of
the electromagnet. This is logical because, an electromagnet only becomes magnetized if a
current is flowing through it, so the larger the current flowing through it, the larger the
magnetic effect should be. The results for the number of turns and current seem to be
somewhat proportional.
Finally, the horse-shoe shaped solenoid exhibited a stronger magnetic force than the
rod shaped one. This is because a horse-shoe is almost a complete loop. Corresponding
magnetic fields on each side of the horse-shoe complement and amplify each other, thus
producing a larger magnetic force.
A clamp & stand could have been used to hold the electromagnet at a fixed distance
from the petri-dish. Therefore, the electromagnet wouldn’t have to be placed in the iron filings.
Also, an iron rod, instead of an iron nail could have been used. This is because a nail is not
completely rod-shaped and this may have affected the results slightly.
Sources of Error:
1. Whilst dropping the iron filings onto the second petri-dish, some may have remained on
the solenoid.
2. There may have been loose connections in the circuit.
3. The power supply may have remained on when making changes to the circuit.
4. The distance between the solenoid and iron filings may have varied for different
recordings.
Precautions:
1. Each time after the current was turned off, the nail was brushed over the petri -dish to
ensure that all the iron filings got into the dish.
2. It was ensured that there were no loose connections in the circuit.
3. Before making any changes to the circuit, it was ensured that the power supply was
switched off first.
4. The electromagnet was dipped inside the iron filings to eliminate the possibility of
varying distances away from the filings.
Conclusion: it was found that all four factors – type of core, no. of turns, current and shape –
affected the strength of an electromagnet.