Electromagnetism

A student used an electromagnet to investigate magnetism.

Figure 12 shows the apparatus.

This is the method used.

1. Turn on the power supply.

2. Record the current on the ammeter.

3. Count the number of paperclips picked up by the electromagnet.

4. Turn off the power supply to release the paperclips.

5. Adjust the power supply and repeat steps 1 to 4 for different values of current.

Draw the circuit symbol for an ammeter in the space below.

Table 1 shows the results.

Complete Figure 13.

You should:

plot the data from Table 1

draw a line of best fit.

The first point has been plotted for you.

The student repeated the investigation using an electromagnet with half as many turns of wire.

How does using fewer turns of wire affect the number of paperclips picked up, for the same value of current?

Tick () one box.

Fewer paperclips will be picked up.

The same number of paperclips will be picked up.

More paperclips will be picked up.

Electromagnets are used in recycling centres to move magnetic materials.

Which two of the following materials are magnetic?

Tick () two boxes.

Cobalt

Copper

Lead

Magnesium

Nickel

Why is an electromagnet more useful than a permanent magnet in a recycling centre?

A student investigated the magnetic effect of an electric current.

The student placed two iron rods inside a rectangular coil.

Figure 9 shows the equipment.

When the power supply is switched on there is a current in the rectangular coil.

Complete the sentence.

When there is a current in the rectangular coil, there is a magnetic field around the coil.

The magnetic field has a similar shape to the magnetic field around

The two iron rods repel each other when there is a magnetic field around the coil.

Explain why.

The two iron rods are replaced with copper rods.

The two copper rods remain stationary when there is a magnetic field around the coil.

Give one reason why.

The student made an electromagnet by: wrapping a coil of wire around an iron bar connecting the coil of wire to a power supply.

The student investigated how the current in the electromagnet affected the strength of the electromagnet.

Figure 10 shows the electromagnet.

The student arranged a newtonmeter and an iron disc above the electromagnet.

Figure 11 shows the equipment.

The power supply is switched off.

Why is the newtonmeter reading 2.0 N?

Tick (✓) one box.

The weight of the electromagnet is 2.0 N.

The weight of the iron disc is 2.0 N.

The weight of the newtonmeter is 2.0 N.

The student switched the power supply on and then increased the current in the electromagnet.

The iron disc was not touching the electromagnet, but the reading on the newtonmeter changed.

Explain why.

The student recorded the readings on the newtonmeter as the current increased.

Figure 12 shows the results.

The student wrapped twice as many turns of wire around the iron bar and repeated the investigation.

Draw a line on Figure 12 to show the expected results.

A student investigated the magnetic effect of an electric current.

The student placed two iron rods inside a rectangular coil.

Figure 1 shows the equipment.

When the power supply is switched on there is a current in the rectangular coil.

Complete the sentence.

When there is a current in the rectangular coil, there is a magnetic field around the coil.

The magnetic field has a similar shape to the magnetic field around

The two iron rods repel each other when there is a magnetic field around the coil.

Explain why.

The two iron rods are replaced with copper rods.

The two copper rods remain stationary when there is a magnetic field around the coil.

Give one reason why.

The student made an electromagnet by: wrapping a coil of wire around an iron bar connecting the coil of wire to a power supply.

The student investigated how the current in the electromagnet affected the strength of the electromagnet.

Figure 2 shows the electromagnet.

The student arranged a newtonmeter and an iron disc above the electromagnet.

Figure 3 shows the equipment.

The power supply is switched off.

Why is the newtonmeter reading 2.0 N?

Tick (✓) one box.

The weight of the electromagnet is 2.0 N.

The weight of the iron disc is 2.0 N.

The weight of the newtonmeter is 2.0 N.

The student switched the power supply on and then increased the current in the electromagnet.

The iron disc was not touching the electromagnet, but the reading on the newtonmeter changed.

Explain why.

The student recorded the readings on the newtonmeter as the current increased.

Figure 4 shows the results.

The student wrapped twice as many turns of wire around the iron bar and repeated the investigation.

Draw a line on Figure 4 to show the expected results.

Permanent magnets have a magnetic field around them.

The Earth has a magnetic field.

Which part of the Earth’s internal structure creates the magnetic field?

Tick (✓) one box.

The crust

The mantle

The outer core

A magnetic compass contains a bar magnet.

Which diagram shows the magnetic field around a bar magnet?

Tick (✓) one box.

A student wrapped insulated wire around an iron bar to make an electromagnet.

Figure 8 shows the electromagnet held in a clamp and connected to a circuit.

When the switch was closed, the electromagnet attracted paper clips.

The student investigated how the number of turns of wire on the iron bar affected the strength of the electromagnet.

This is the method used.

1. Wrap 20 turns of wire around the iron bar.

2. Hold the paper clips near the bottom of the electromagnet.

3. Close the switch.

4. Count the number of paper clips the electromagnet picks up.

5. Open the switch.

6. Repeat steps 1 to 5, but with more turns of wire around the iron bar.

The student used the same value of current throughout the investigation.

What type of variable was the current?

Tick (✓) one box.

Control variable

Dependent variable

Independent variable

Table 4 shows the results.

When there was no wire wrapped around the iron bar, no paper clips were picked up.

Draw a ring around the anomalous result in Table 4.

The student did not take another reading to replace the anomalous result.

What did the student do with the anomalous result when calculating the mean?

Figure 9 is a graph of the results.

How many paper clips would be picked up when 70 turns of wire are wrapped around the iron bar?

The investigation was repeated using a larger current.

Draw a line on Figure 9 to show the expected results.

A student investigated magnetic fields.

Figure 24 shows a cube-shaped magnet and a magnetic compass.

Describe how the student could identify the poles of the magnet using the magnetic compass.

Figure 25 shows a wire with a current in it.

The arrow shows the direction of the current in the wire.

There is a magnetic field around the wire.

Figure 26 shows the wire when the current is in the opposite direction to Figure 25

Complete Figure 26 to show the magnetic field around the wire.

Figure 27 shows an electromagnet made from a coil of wire wrapped around an iron core.

Figure 27

When the switch is closed, there is a magnetic field around the electromagnet.

Label on Figure 27:

The student opened the switch and placed a paper clip near the electromagnet.

When the switch was closed, the paper clip accelerated towards the electromagnet.

Use the Physics Equations Sheet to answer questions 11.4 and 11.5.

Write down the equation which links acceleration (a), mass (m) and resultant force (F).

Explain why the acceleration of the paper clip changes as the paper clip moves towards the magnet.

Figure 4 shows a student holding a magnet near another magnet.

Which of the following describes the force between the two magnets?

Tick (✓) one box.

An electrostatic force

A frictional force

A non-contact force

Figure 5 shows three metal bars, 1, 2 and 3.

Two of the bars are permanent magnets and the other bar is made of iron.

The student recorded whether the bars were attracted or repelled when different ends were placed near to each other.

Which metal bars are magnets?

Tick (✓) one box.

Bars 1 and 2

Bars 2 and 3

Bars 3 and 1

Give a reason for your answer.

When there is a current in a wire there is a magnetic field around the wire.

Which diagram shows the magnetic field around the wire?

Tick (✓) one box.

Figure 6 shows the equipment a student used to investigate the strength of an electromagnet.

This is the method used.

1. Wrap insulated wire around an iron bar.

2. Connect the wire to a battery to make an electromagnet.

3. Hold paperclips near to the bottom of the electromagnet.

4. Count the number of paper clips the electromagnet picks up.

5. Repeat steps 3 and 4 for different values of current.

Give one way the size of the current in the circuit in Figure 6 can be changed.

Figure 7 shows the results.

Draw a line of best fit on Figure 7.

The student used an interval of 2 A for current in the investigation.

Explain why the student should have used a smaller interval for current.

Figure 8 shows an electromagnet being used to separate metals to be recycled.

Explain the advantage of using an electromagnet instead of a permanent magnet.

Figure 7 shows part of the magnetic field around a bar magnet.

Figure 7

Complete Figure 7 to show the magnetic field around the bar magnet.

You should:

• draw one more magnetic field line

• show the direction of the magnetic field.

A student made an electromagnet from a metal nail and a coil of wire.

Figure 8 shows the electromagnet held in a clamp and connected to a circuit.

When the switch was closed, the electromagnet attracted paper clips.

Which metal should be used for the nail?

Tick (✓) one box.

The student varied the number of turns of wire around the nail.

The student recorded how many paper clips the electromagnet could hold.

Table 1 shows the results.

Predict value X in Table 1.

The student increased the resistance of the variable resistor.

What is the circuit symbol for a variable resistor?

Tick (✓) one box.

Complete the sentences.

Choose answers from the box.

Each answer may be used once, more than once or not at all.

When the resistance of the variable resistor was increased, the current in

the electromagnet.

When the resistance of the variable resistor was increased, the number of paper

clips the electromagnet could hold.

Figure 9 shows an electromagnet being used at a scrapyard.

Give two advantages of using an electromagnet to sort scrap metal compared with using a permanent magnet.