electromagnetic induction

the current produced by a magnet

The device with the pointer in the Figure 1.1 is an ammeter. It measures the current that flows through the wire. The faster the magnet or coil moves, the greater the amount of current that is produced. If more turns were added to the coil or a stronger magnet were used, this would produce more current as well. The Figure 1.2 shows the direction of the current that is generated by a moving magnet. If the magnet is moved back and forth repeatedly, the current keeps changing direction. In other words, alternating current (AC) is produced. Alternating current is electric current that keeps reversing direction.

textbook_image

textbook_image

what is electromagnetic induction

Electromagnetic induction is the process of generating electric current with a magnetic field. It occurs whenever a magnetic field and an electric conductor, such as a coil of wire, move relative to one another. As long as the conductor is part of a closed circuit, current will flow through it whenever it crosses lines of force in the magnetic field. One way this can happen is illustrated in the Figure 1.1. The sketch shows a magnet moving through a wire coil. Q: What is another way that a coil of wire and magnet can move relative to one another and generate an electric current? A: The coil of wire could be moved back and forth over the magnet.

how electromagnetic induction is used

Two important devices depend on electromagnetic induction: electric generators and electric transformers. Both devices play critical roles in producing and regulating the electric current we depend on in our daily lives. Electric generators use electromagnetic induction to change kinetic energy to electrical energy. They produce electricity in power plants. Electric transformers use electromagnetic induction to change the voltage of electric current. Some transformers increase voltage and other decrease voltage. Q: How do you think the girl on the exercise bike in the opening photo is using electromagnetic induction? A: As she pedals the bike, the kinetic energy of the turning pedals is used to move a conductor through a magnetic field. This generates electric current by electromagnetic induction.

instructional diagrams

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questions

what is needed for electromagnetic induction to occur?

a) electric conductor

b) magnetic field

c) voltage source

-->  d) two of the above

you can generate electric current by moving a permanent magnet inside a coil of wire.

-->  a. true

b. false

you can produce more current by electromagnetic induction if you

a) use a wire with more turns in the coil.

b) move the magnet or wire coil more quickly.

c) use a stronger magnet.

-->  d) any of the above

electromagnetic induction produces only direct current.

a. true

-->  b. false

electromagnetic induction is used in electric

a) motors.

-->  b) generators.

c) doorbells.

d) two of the above

diagram questions

No diagram questions associated with this lesson