Electricity & Magnetism Study Island

What is the relationship between electricity and magnetism?

An electric current creates a magnetic field, and a moving magnet creates a current.

The arrows in the following diagrams represent the direction of magnetic domains in an iron bar. Which bar is magnetized?

Bar with arrows facing 1 direction

The electromagnet in which of the following diagrams will generate a magnetic field that periodically reverses its orientation?

Diagram with s inside of a circle

The following diagram shows a permanent bar magnet. What would happen to the magnetic field if the bar magnet were cut in half along the center line?

Each half would have a north pole and a south pole.

Many buildings and homes are equipped with magnetic locks. An electromagnet holds a metal door shut with the force of its attraction.Some of these doors have a button placed nearby. Shortly after the button is pushed, the door is able to open. What does this button most likely do?

It stops the flow of electricity to the electromagnet for a certain amount of time.

When someone speaks into a microphone, the sound waves reach a small diaphragm inside. The diaphragm moves slightly in response to the sound waves hitting it. How is the movement of the diaphragm most likely translated into electrical impulses?

The diaphragm is wrapped in a coil of current-carrying wire, which produces a changing magnetic field as it moves

The arrows in the diagram below show the direction of the magnetic field lines created by two magnets. How do the field lines shown in the diagram demonstrate the repulsion between like poles?

The field lines of like poles diverge, thus showing their repulsion of one another.

The arrows in the diagram below show the direction of the magnetic field lines created by two magnets. How do the field lines shown in the diagram demonstrate the attraction between opposite poles?

The field lines of opposite poles connect, thus showing their attraction to one another.

The magnetic domains of the iron bar shown below have aligned as shown. The magnetic domains of the iron bar shown below have aligned as shown

The iron bar was exposed to an external magnetic field

For his science fair project, Edgar wants to create a simple generator to produce electricity. To do this, he places a magnet in the middle of coils of wire that are attached to a light bulb. After completing his project, however, the light bulb does not light up. Why?

The magnet needs to be in motion, not stationary.

The following diagram shows an electromagnet, with the current flowing from A to B. What would happen to the magnetic field if the direction of the current was reversed?

The magnetic field would reverse

The following diagram shows two bar magnets. Which of the following describes the interaction between the two magnets?

The magnets will repel each other.

A conducting wire is placed inside a magnetic field. When the wire is rotated, an electrical current runs through it. Which of these best explains why the wire needs to be rotated?

The movement of the wire within the magnetic field produces the current

Joaquin's bicycle has a headlight that requires no batteries. If he pedals slowly, the light flickers. If he pedals quickly, the light gives off a steady, bright light. How does the headlight get its energy?

There are a few magnets attached to Joaquin's front tire, and the light is attached to a coil of wire.

Which of the following will result in an electric current flowing through a wire?

a bar magnet being spun near a coiled wire

A very basic electric generator is pictured below. When the crank is turned, the light bulb lights up.If the permanent magnets are stationary, what must be located in between them?

a coil of conducting wire that spins when the crank is turned

Marcella keeps a "kinetic flashlight" in her car for emergencies. To charge the flashlight, Marcella shakes it rapidly. She can hear something inside moving back and forth. After being shaken for a while, the flashlight will turn on for a time. One day Marcella opens up the flashlight and sees a coil of wire firmly attached inside it. What is inside the flashlight and moves back and forth when Marcella shakes it?

a permanent magnet

Alberto is studying how the number of coils in an electromagnet's solenoid affects the strength of the magnet. He recorded his results in the table below. What pattern does Alberto's data show?

adding one coil to the solenoid doubles the magnet's strength

How is an electromagnet different from a permanent magnet, such as a horseshoe magnet?

all of these

Industrial magnets, such as the one below, can be used to attract large amounts of scrap metal and then release it elsewhere. Which of the following causes the magnetic force between the magnet and the scrap metal?

an electric current running through the industrial magnet

An outside source of energy is used to spin a permanent magnet. The magnetic field of the spinning magnet causes electrons to move in a coil of wire. This produces an alternating current in the wire.What device best fits the description above?

an electric generator

An induction stove works by inducing an electric current in a metal pan. The pan rests on the surface of the induction stove, and beneath the surface is a coil of current-carrying wire. When the burner is turned on, AC current flows through the coil, which generates a changing magnetic field. The pan responds to this changing magnetic field by carrying a changing electric current. The resistance of the pan causes it to heat up and cook its contents. Why would food in a glass pot not cook on an induction stove?

because glass is an electrical insulator

How might an electric force be applied to the electrons in a coil of copper wire?

by moving a magnet past the wire

Consider the electrical transformer shown below. A current enters and exits on the left, through the yellow wire. The blue wire on the right is part of a separate circuit. Both wires are wrapped around the transformer core, which is made of a conducting material. No current flows between either wire and the transformer core. If the yellow wire carries a constant direct current, the blue wire will

carry no current.

Motors contain electromagnets that transform

electrical energy into mechanical energy.

Which lab tool is used to convert mechanical energy into electrical energy?

generator

A current is passing along a wire. Which of the following will increase the strength of the magnetic field around the wire?

increasing the current through the wire

The diagram below represents an electromagnet. Which of the following changes would increase the strength of the magnetic field?

increasing the number of coils

The diagram below represents an electromagnet. Which of the following materials would generate the strongest magnetic field if used as the core?

iron

Consider the electrical transformer shown below. An alternating current enters and exits on the left, through the yellow wire. The blue wire on the right is part of a separate circuit. Both wires are wrapped around the transformer core, which is made of a conducting material. No current flows between either wire and the core. The voltage across the blue circuit is

less than the voltage across the yellow circuit.

An electric current is flowing through a copper wire. Which type of force can be produced by the flow of the current?

magnetic

Which lab tool is used to convert electrical energy into mechanical energy?

motor

An electromagnet is a device that uses an electric current to produce a magnetic field.Electromagnets are typically composed of a piece of metal wrapped with wire and connected to a battery. The battery provides the electric current, and the loops or coils of wire enhance the magnetic field. The more loops there are, the stronger the magnetic field.When electric current flows through the electromagnet, the metal core becomes magnetized, so it possesses a north pole and a south pole.Motors place electromagnets inside of permanent magnets as shown below. However, motors are designed so that the polarity of the electromagnet constantly flips. That is, the north pole becomes the south pole, and the south pole becomes the north pole, every time the electromagnet turns 180 degrees.Why is it designed this way?

so the electromagnet will continuously turn

A temporary magnet is produced by exposing an iron bar to an external magnetic field.Which of the diagrams above shows the most likely alignment of the iron bar's magnetic domains after the external magnetic field is switched off?

the diagram with crazy direction arrows

When is a magnetic field generated?

whenever a current is passing through a wire

Tape recorders contain strips of thin plastic tape, which are covered in a layer of very fine iron dust. The iron dust reacts to a changing magnetic field and slightly rearranges itself on the tape, thereby recording the pattern generated by the changing magnetic field.How is this changing magnetic field most likely produced?

with an electromagnet

Which of the following will strengthen the magnetic field produced by the electromagnet shown above?

wrapping more coils of wire around the core

Many home appliances include a device known as a ground fault interrupter. This is a safety device that is designed to interrupt the flow of electricity to an appliance when it is not functioning properly. The interrupter works by monitoring the flow of electricity into and out of the appliance, which runs on AC. If the flow in does not equal the flow out, the appliance is not functioning properly and could be dangerous to touch.The device consists of a conductive coil of wire that is wrapped in an iron ring. The coil is connected to the circuit breaker, and the ring surrounds the wires exiting and entering the appliance. According to this information, about how much electric current should flow through the coil when the appliance is functioning properly?

zero current