Electromagnets
Lesson 5 / 5
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Waxaan sharxi karaa sida loo sameeyo magnet iyadoo la isticmaalayo qulqulka korontada.
Introduction
In this lesson: I can describe how to make a magnet using an electric current. When there is an electric current in a wire, there is a magnetic field around the wire. When there is an electric current in a coil of wire, the magnetic field around each loop adds to make a stronger field.
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Quizzes
1. Which of the following metals are magnetic?
- Correct answer:iron
- sodium
- Correct answer:cobalt
- copper
2. Which statement about the magnetic field lines round a bar magnet is correct?
- They point out of both the N–pole and the S–pole.
- They point into both the N–pole and the S–pole.
- Correct answer:They point out of the N–pole and into the S–pole.
- They point out of the S–pole and into the N–pole.
3. Earth's magnetic field behaves as if there is a magnet inside the planet. Which of the following statements about this imaginary magnet is correct?
- Correct answer:The S–pole of the magnet is at Earth's North Pole.
- The S–pole of the magnet is at Earth's South Pole.
- The S–pole of the magnet is at Earth's equator.
- The N–pole of the magnet is at Earth's equator.
4. Where is Earth's magnetic field strongest?
- at the equator
- Correct answer:at the north and south poles
- at the Bermuda triangle
- on top of the highest mountain
5. Which of the following will not deflect a magnetic compass needle?
- an iron nail
- a steel fork
- a nickel coin
- Correct answer:an electrostatically charged balloon
6. Which of the following statements about the poles of magnets is correct?
- A north pole will attract a north pole.
- Correct answer:A north pole will attract a south pole.
- A north pole will repel a south pole.
- A south pole will attract a south pole.
1. Which of the following would not cause a compass needle to deflect?
- Correct answer:an electrostatically charged plastic ruler
- a copper wire carrying current
- Earth's magnetic field
- an iron rod
2. Which of the following is not needed to make a strong electromagnet?
- an iron rod
- insulated wire
- a power supply
- Correct answer:paperclips
3. Why do paper clips fall off the electromagnet when the current is turned off?
- The magnetism has returned to the power pack.
- Correct answer:There is no current in the coil.
- The wire has overheated.
- The paperclips repel the core.
4. Which of the following changes will not make an electromagnet stronger?
- Increasing the current in the wire.
- Increasing the voltage across the wire.
- Increasing the number of turns in the coil.
- Correct answer:Increasing the number of paperclips.
5. Which of the following will increase the strength of the magnetic field in a coil of insulated wire?
- Increasing the diameter of the coil.
- Increasing the resistance of the wire in the coil.
- Correct answer:Putting an iron core in the coil.
- Putting a copper core in the coil.
6. What is the shape of the magnetic field lines caused by a straight, current–carrying wire?
- spherical around the wire
- straight and away from the wire
- Correct answer:circular around the wire
- straight and in the same direction as the wire
What pupils see
The same lesson as a pupil sees it. You can set any section as work on its own.
- IntroductionPrepare
- Starter quizActivate · 6 questions
- Lesson videoLearn
- Exit quizCheck · 6 questions