Magnets, magnetic fields and electromagnets
Grade 8 Science Worksheet - Challenge Me
Circle the best answer, or write your answer on the line.
Read this first
Teacher's electromagnet test (example data)
coils paper clips lifted 10 2 20 9 30 16 40 23 The clips lifted keep rising in equal steps. How many clips would Bo's electromagnet lift with 60 coils?
Jun wants to test whether more batteries make an electromagnet stronger. Which plan is best?
- Use 1, 2 and 3 batteries with 10, 20 and 30 coils, to save a lot of time
- Use 1, 2 and 3 batteries, but with a different nail each time
- Use 1, 2 and 3 batteries once each, and then trust the first results
- Use 1, 2 and 3 batteries with the same coil and nail, repeating each
Use this
Investigation card (test results). Changed: number of coils. Measured: paper clips lifted. Kept the same: same nail, same battery, one trial for each setup. 10 coils: 3. 20 coils: 7. 30 coils: 11.
Which conclusion is best supported by this test, Kira?
- Coils made no difference, since the numbers are small
- More coils lifted more clips here; each setup needs repeating
- Shown for any nail and any battery, so no repeat is needed
- More coils lifted fewer clips, so fewer coils are better
Use this
Investigation card (test results). Changed: coils and core. Measured: paper clips lifted. Kept the same: 1 battery. 10 coils, no core: 2. 30 coils, iron nail: 19.
Luz says the iron nail caused the jump in clips. Why is that not supported by this test?
- Coils and core both changed, so either could explain the jump
- Nails do not change an electromagnet
- The test should have changed the batteries as well, to test everything
- The nail should have been aluminum
Which observation is the strongest evidence that a magnetic field acts between objects that are not touching, Milo?
- A compass needle turns when a magnet is near but not touching
- A magnet sticks to a metal fridge door when it touches it
- A paper clip stays stuck to a magnet once it touches it
- A bar magnet feels heavy for its size when it is lifted
Which model best explains why more coils make an electromagnet stronger, Noah?
- Each loop adds its own magnetic field, and the fields add up
- More wire is heavier, so it pulls harder on the clips
- More coils block the iron core's field from reaching clips
- More coils store more of the battery's energy for later
An iron nail lifts 15 clips; with no core the coil lifts 4. Which model best explains the nail's effect, Pia?
- Iron is heavy, so it drags the clips up
- Iron stores the battery's electricity
- The coil's field magnetizes the iron, which adds its own field
- Iron is a permanent magnet already, so it works without a battery
Electromagnet with an iron nail (example data)
batteries paper clips lifted 1 15 2 25 3 33 Ren says doubling the batteries doubles the clips lifted. What does the table show?
- Agree: 2 batteries gave more clips than 1 battery did
- Disagree: 15 to 25 is about 1.7 times, not 2 times
- Disagree: batteries make no difference to the clips
- Agree: adding more batteries doubles the clips each time
Pull on a steel ball (example data)
distance from the magnet (cm) pull (N) 3 6.0 6 1.5 12 0.4 Tala says the pull at 6 cm is half the pull at 3 cm. Is that right?
- No: 1.5 N is a quarter of 6.0 N, not a half
- Yes: 1.5 N is small compared with 6.0 N
- No: the pull is the same at both distances
- Yes: 6 cm is double 3 cm, so the pull halves
Compass at the coil's right end (example data)
battery connection needle's north end points normal away from the coil reversed toward the coil Zee says an electromagnet's poles are fixed, like a bar magnet's. What does the table show?
- Agree: the same coil is the same kind of magnet each time
- Disagree: reversing the current swapped the poles
- Disagree: the poles disappeared when it was reversed
- Agree: the compass needle just points north anyway