Physics Ch14

The south pole of a bar magnet is moved toward a short helical coil of wire (solenoid) along the axis of the coil. The coil has 100 turns and the ends of the coil are connected to form a closed circuit. If the coil is replaced with a single loop of wire of the same diameter, and the magnet is moved exactly as before, the magnet experiences a force that is

repulsive and 100 times smaller.

A transformer is used to either increase or decrease the voltage in an AC circuit. When the output voltage is greater than the input voltage of a transformer then

the power output is the same as the power input.

A little magnetic compass has a needle whose tips are clearly labeled N and S. The compass is placed next to a single circular loop of wire lying flat on a wooden table. The current in the loop is clockwise. What happens?

None of these.

A bar magnet and an electrically polarized object are placed next to each other on a table. What happens?

Nothing happens.

The sketch below shows a bar magnet in a loop of wire with the bar perpendicular to the plane of the loop. The left-hand side shows the magnet being spun around its long axis while on the right side the magnet is turned end-over-end. Which case creates a larger induced current in the loop?

The right-hand side.

What would happen if you had a car made completely of plastic, with no metal parts, and you drove over a vehicle sensor embedded in the road surface?

The sensor would not notice you or your vehicle, and you'd be stuck at the red light.

A loop of wire is oriented in the magnetic field as shown below (the plane of the loop is perpendicular to the direction of the magnetic field). Which of the following is true?

There will be an induced current if the loop is moved either up or down.

A permanent magnet is produced when

magnetic fields of large groups of individual atoms are permanently aligned.

Magnetic fields affect

only electric charges in motion.

The south pole of a bar magnet is moved toward a short helical coil of wire (solenoid) along the axis of the coil. The coil has 100 turns and the ends of the coil are connected to form a closed circuit. If the coil is replaced with a single loop of wire of the same diameter, and the magnet is moved exactly as before, the current induced in the loop is

100 times smaller.

A transformer is to be used to step up voltage from an alternating current source from 110 V to 660 V. If the primary has 120 turns, then the number of turns in the secondary is

720.

You see a positively charged helium ion in space, and it is at rest with respect to your spacecraft. Since you are studying for the final exam, you decide to experiment: You push the N pole of a bar magnet closer to the helium ion. What happens to the helium ion?

It experiences a magnetic force and moves off.

The south pole of a bar magnet is moved toward an aluminum ring, along the axis of the ring. As the magnet approaches, the changing magnetic flux induces an electric current in the ring that, when seen from the bar magnet, corresponds to positive charge carriers flowing

clockwise.

Think of a closed rectangular loop of wire around the edge of this page. A magnetic field perpendicular to the page points upward and increases in strength in a certain time. During this time the conventional current induced in the loop will be

clockwise.

Imagine that this classroom contains a constant magnetic field that points from the front to the back. In front of you a negative charge is slowly moving horizontally to your left. As you watch, the magnetic force on the charge

deflects the charge into a counterclockwise vertical circle.

Imagine a magnetic field pointing into the plane of this page. An electron moves across the paper from left to right. The direction of the magnetic force on the electron will be

in the plane of the paper and toward the bottom of the page.

If an electron is placed at rest near a bar magnet, the electron will

not move at all.

A horizontally moving positive sodium ion enters a magnetic field that points up. The magnetic force pushes the charge out of its original path.When viewed from the perspective of the charge, what direction will the magnetic force point?

Right, out of the page.

A battery is causing a large current in a horizontal solenoid (helical coil of wire). A horizontal bar magnet is held at rest nearby, aligned with the axis of the solenoid, south pole closest to the solenoid. The bar magnet is being repelled by the solenoid. Which of the following statements is true of the conventional current in the solenoid?

The current in the solenoid is flowing clockwise as seen from the bar magnet.

In outer space, you observe a straight stream of electrons flowing past you at 14.5 miles per second, about the same speed that Mars moves on its orbit around the sun.You maneuver your spacecraft to face the current so that the electrons are moving from left to right and so that you are 10 m from the stream. Now you fire your rockets and boost your speed so that you are also moving at 14.5 miles per second, exactly at the same speed and direction as the electrons. In what direction does a compass needle point now?

You observe no magnetic field.

The magnetic pole near the Earth's north geographic pole actually has to be

an S pole, because it attracts the N pole of your compass needle.

Two identical coils of wire are placed on a single horizontal wooden broom handle. The coils are separated by a few centimeters. We now run identical currents in the same direction through each coil. The coils experience

an attractive magnetic force.

Two particles move into a magnetic field. They enter moving at the same speed and direction. The magnitude of the charge on each is known to be the same. One particle moves to the right and the other to the left upon entering the field, the one on the left moving in a larger circle than the one on the right. From this we can say that

the leftward moving particle has more mass but we can't say anything about its charge.

In outer space, you observe a straight stream of electrons flowing past you at 14.5 miles per second, about the same speed that Mars moves on its orbit around the sun.You maneuver your spacecraft to face the current so that the electrons are moving from left to right and so that you are 10 m from the stream. In what direction does a compass needle point?

up

Two current-carrying wires are parallel to one another and separated by 1 cm. If the distance between them is increased to 2 cm the new force will be what factor times the original force?

½