Ch. 9 homework

An ideal transformer has 50 turns in the primary and 500 turns in the secondary. An input of 12 V will produce an output of

120 V

The voltage across the input terminals of a transformer is 110 V. The primary coil has 50 loops and the secondary coil has 100 loops. The output is

220 V

An electronic game requires 6 V for operation. With a transformer it can be powered by a 120-V outlet. If the primary has 500 turns, the secondary has

25 turns

An electronic game requires 6 V for operation. With a transformer it can be powered by a 120-V outlet. If the primary has 500 turns, the secondary has

440 W

A transformer has an input of 6 V and an output of 42 V. If the input is changed to 12 V, the output would be

84 V

What are the basic differences and similarities between a generator and an electric motor?

A generator converts mechanical energy to electrical energy; a motor converts electrical energy into mechanical energy.

Why is iron magnetic and wood not magnetic?

Atoms in wood are not so strongly magnetic that they organize into domains as iron atoms do

The metal detectors that travelers walk through at airports operate via

Faraday's Law

When a bar magnet is thrust into a coil of wire, a greater voltage is induced with

a greater number of loops in the coil and a stronger bar magnet. and faster thrusting motion.

Surrounding every moving electron is

a magnetic and electric field

A compass needle in a magnetic field experiences

a torque

A galvanometer calibrated to read potential difference is

a voltemeter

A friend says that changing electric and magnetic fields underlie the production of light.

agree with your friend

A galvanometer calibrated to read current is

an ammeter

Like kinds of magnetic poles repel while unlike kinds of magnetic poles

attract

When a current-carrying wire is bent into a loop, its magnetic field inside the loop

becomes concentrated

Compared with the current in the primary coil of a transformer, the current in the secondary coil

can be greater or less

The magnetic field lines about a straight current-carrying wire are

circular

Electromagnetic induction is employed in

computers, mobile phones, and credit card readers

A common electromagnet consists of a

current-carrying coil with a piece of iron inside.

The principal difference between a step-up and step-down transformer is

different ratios of turns for each set of loops or coils.

When an electron passes through the magnetic field of a horseshoe magnet, the electron's

direction of motion is changed

Moving electric charges are surrounded by

electric and magnetic fields

Surrounding every stationary electron is

electric field

The fact that a force is exerted on a current-carrying wire when in a magnetic field is employed in

electric meters and motors

Faraday's law describes

electromagnetic induction

What any type of field generation cannot create is

energy

Power is the rate at which

energy is transferred

Compared with the huge force that attracts an iron tack to a strong magnet, the force that the tack exerts on the magnet is

equally huge

An iron nail is attracted

equally to either pole of a magnet

Magnet A has twice the magnetic field strength of magnet B and 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 device that transforms mechanical energy to electrical energy is a

generator

If you break a bar magnet in half you'll

have two magnets

Magnetic domains normally occur in

iron

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

iron rod

Compared with a motor, a generator is

its opposite

Electric and magnetic fields combine to produce

light

Wood does not have magnetic properties because it contains no

magnetic domains

The ultimate source of all magnetism is

moving electric charge

Several paper clips dangle from the north pole of a magnet. The induced pole in the bottom of the lowermost paper clip is a

north pole

The minimum or no magnetic force on a moving electron occurs for motion

parallel to the magnetic field.

The induced electric and magnetic fields of Maxwell are

perpendicular to each other

Maximum magnetic force occurs when electrons move

perpendicular to the magnetic field direction.

A strong magnetic field easily penetrates

plastic coatings and human flesh

The rate at which a transformer transfers energy is called

power

Since magnetic force on a moving electron is always perpendicular to its direction of motion, magnetic force is unable to change an electron's

speed

Magnetism is due to the motion of electrons as they

spin on their axes. and move around the nucleus.

A topic that most underlies electrical studies and all of physics is

the conservation of energy

Voltage produced by a generator alternates because

the magnetic field that produces it alternates.

The magnetic field inside a current-carrying coil increases when

the number of loops of wire in the coil increases and an iron core is inserted and current is increased.

Compared with the power input to an ideal transformer, the power output is

the same

When a bar magnet is broken in half, the strength of the four new poles relative to pole strength before breaking is

the same

When a bar magnet is thrust at the same speed into a coil having twice the number of loops, the induced voltage is

twice as much

Every magnet contains at least

two poles

A step-up transformer in an electrical circuit can step up

voltage

An efficient step-down transformer decreases

voltage

The frequency with which a magnet plunges into and out of a wire coil equals the frequency of the induced

voltage and current

The energy source for a generator may be

wind and steam from a turbine and a waterfall.

A magnetic field exists in a current-carrying coil of wire

with or without a contained piece of iron.