Understand the Factors that Affect the Strength of an Electromagnet

Electromagnets are a type of magnet that we can switch on and off using electricity. 

 

 

Multiple factors affect the strength of an electromagnet, including the number of turns on the coil of wire. Increasing the number of turns increases the strength of the magnet.  

 

Additionally, using an iron core, like the iron nail in the image above, also increases the strength of the electromagnet. 

 

But what about the current flowing in the circuit? Let's find out how that affects the strength of the electromagnet!

 

 

To recap - the current in a circuit tells us the rate of flow of electrical charge in a circuit.

In other words, the more electrons there are carrying charge per second, the greater the current. 

 

We measure current in Amps, using an ammeter. 

 

 

Paper clips are made out of steel, a magnetic material. The more paper clips a magnet can pick up, the stronger it is! We can use this idea to test the strength of a magnet - the more paper clips it picks up, the stronger it is. 

 

Let's set up a series circuit with a variable power supply, an ammeter, and the wire to wrap around the iron core to make the electromagnet. 

 

 

In our experiment, the independent variable will be the current flowing in the circuit. We can vary the current using the power supply. We can measure the current with the ammeter. 

 

The dependent variable will be the number of paper clips picked up by the electromagnet. 

 

Method

1. Create an electromagnet by connecting the circuit as shown in the diagram above

2. Spread many paper clips on a clear surface, ensuring the clips are not stuck together

3. Vary the power supply until the current measured in the ammeter is 0.5 A

4. With the electromagnet turned on, see how many paper clips can be picked up by placing the electromagnet gently on the pile of paper clips

5. Disconnect the electromagnet to allow it to cool down

6. Reconnect the electromagnet, and vary the power supply until the current is 1 A

7. See how many paper clips can be picked up now

8. Repeat this process with an interval of 0.5 A, five times

 

 

We need to keep some control variables constant to make this a fair test. 

 

First, we need to keep the same number of turns on the wire each time, so that it won't affect the results. 

Second, we need to make sure the electromagnet does not get too hot because this can affect the resistance and the current in the circuit. 

 

What do you predict the results of the experiment will be?

 

Here are some example results:

 

Current (A)	Number of paper clips
0.5	2
1.0	4
1.5	7
2.0	9
2.5	10

 

We can write a conclusion based on these results. 

 

As the current in the wire increases, the number of paper clips picked up increases. This tells us that increasing the current in the wire increases the strength of the electromagnet. 

 

Now let's try some questions!