Magnetism

The output power of an ideal transformer is

equal to the input power.

Which of the following expressions shows the correct relationship between 1 T (1 tesla) and other common units?

1 N/(Am)

A step-up transformer has a ratio of one to ten. Neglecting slight losses, if 100 W of power go into the primary coil, the power coming from the secondary coil is

100 W.

Four amperes of current exist in the primary coil of a transformer. The voltage across the primary coil is 110 V. What is the power output of the secondary coil?

440 W

A certain transformer doubles input voltage. If the primary coil has 10 A of current, then the current in the secondary coil is

5 A

If we think of the Earth as a magnet, its north (-seeking) pole is nearest

Australia

Which of the following options can be used to generate electricity?

Change the magnetic field strength around the circuit loop. Change the orientation of the circuit loop with respect to the magnetic field. Move the circuit loop into and out of a magnetic field.

Magnet A has twice the magnetic field strength of Magnet B and at a certain distance pulls on magnet B with a force of 100 N. The amount of force that magnet A exerts on magnet B is

exactly 100 N.

A current in a long, straight wire produces a magnetic field. These magnetic field lines

form circles that go around the wire.

A device that transforms mechanical energy into electrical energy is a

generator.

Thrust a magnet into a coil of wire and the coil

has a current in it. becomes an electromagnet.

Figure 24-30 shows the end view of an electromagnet with current flowing through it. What is the direction of the magnetic field inside the loop?

into the page

Magnetic domains normally occur in

iron

In a magnetized substance, the domains

line up mainly in one direction.

Power is transmitted at high voltages because the corresponding current in the wires is

low so that overheating of the wires is minimized.

A current can be induced in a closed circuit without the use of a battery or an electrical power supply by moving the circuit through a

magnetic field.

Which conversion process is the basic function of the electric generator

mechanical energy to electrical energy

A device that transforms electrical energy to mechanical energy is a

motor.

The source of all magnetism is

moving electric charge.

A step-up transformer increases

neither power or energy.

Outside a magnet, magnetic field lines are conventionally drawn from

north to south.

The force on an electron moving in a magnetic field will be the largest when its direction is

perpendicular to the magnetic field direction.

When a bar magnet is thrust into a coil of copper wire, the coil tends to

repel the magnet as it enters.

The magnetic field strength inside a current-carrying coil will be greater if the coil encloses a

rod of iron.

Which of the following situations is not true for magnets?

Unlike poles repel each other.

Which compass needle orientation in the figure above might correctly describe the magnet's field at that point?

a (this is the one on the left pointing away and slightly up on the North side)

When there is a change in the magnetic field in a closed loop of wire

a current is created in the loop of wire. a voltage is induced in the wire. electromagnetic induction occurs.

What is the direction of the force acting on a current-carrying conductor lying in a magnetic field?

It is at right angles to both the direction of the magnetic field and the direction of the current.

All of the following statements about magnetic field lines around a permanent magnet are true except which one?

Magnetic field lines appear to end at the north pole of a magnet.

All of the following are ways to induce a voltage in a loop of wire except which one?

Move the loop parallel to a magnetic field.

A wire moving at right angles to a magnetic field has NO induced voltage

None of the above choices are correct.

Which of the following statements about Earth's magnetic field is true?

The geographic South Pole of Earth and Earth's magnetic north pole are relatively close to each other.

Where is the magnitude of the magnetic field around a permanent magnet greatest?

The magnitude is greatest close to the poles.

Moving electric charges will interact with

an electric field or a magnetic field.

An electric motor is very similar to

an electric generator.

If a steady magnetic field exerts a force on a moving charge, that force is directed

at right angles to the direction of the field.

If a steady magnetic field exerts a force on a moving charge, that force is directed

at right angles to the direction of the motion.

Transformers use ac so there will be the required

change in magnetic field for operation.

Voltage can be induced in a wire by

changing the current in a nearby wire. moving the wire near a magnet. moving a magnet near the wire.

Magnetic field lines about a current-carrying wire

circle the wire in closed loops.

A microscopic magnetic region composed of a group of atoms whose magnetic fields are aligned in a common direction is called a(n) ____. In most materials, when these groups are randomly distributed, the substance will show ____ magnetism.

domain; no

A current-carrying wire is placed between the poles of a magnet, as shown in Figure 24-33. What is the direction of the force on the wire?

downwards

In which direction, in relation to a magnetic field, would you run a current-carrying wire so that the force on it, resulting from the field, is minimized or even made to be zero?

run the wire parallel to the magnetic field

A long, straight, current-carrying wire runs from north to south. A compass needle placed underneath the wire points with its N-pole toward the west. In what direction is the current flowing through the wire?

south to north

A solenoid is in an upright position on a table. A counterclockwise current of electrons—when viewed from above—causes the solenoid to have a ____ magnetic pole at its bottom end. If a compass is placed at the top of the solenoid, the north pole of the compass would be ____.

south; repelled

An iron rod becomes magnetic when

the net spins of its electrons are in the same direction.

If a magnet is pushed into a coil, voltage is induced across the coil. If the same magnet is pushed into a coil with twice the number of loops,

twice as much voltage is induced.

A transformer actually transforms

voltage.

Under which of the following conditions is the net magnetic force on a charged particle equal to zero?

when the particle is stationary when the particle is not charged when the particle is moving parallel to the magnetic field