Test Part 5

A certain transformer doubles input voltage. If the primary coil has 10 A of current, then the current in the secondary coil is A) 5 A. B) 2 A. C) 10 A. D) 25 A. E) none of these

5 A

A wire moving at right angles to a magnetic field has NO induced voltage A) if it is moving slowly. B) if it is moving very fast. C) if it is made of copper. D) if the wire is covered with insulation. E) None of the above choices are correct.

None of the above choices are correct.

The principal advantage of ac power over dc power is that A) ac circuits are safer. B) ac voltage oscillates while dc voltage does not. C) ac voltage can be transformed via conventional transformers. D) more energy is dissipated during transmission. E) ac circuits multiply power more easily.

ac voltage can be transformed via conventional transformers.

Moving electric charges will interact with A) an electric field or a magnetic field. B) only an electric field. C) only a magnetic field. D) none of these

an electric field or a magnetic field.

Rapid change of a magnetic field induces A) a magnetic field of greater magnitude. B) an electric field. C) a magnetic field of the same magnitude.

an electric field.

An electric motor is very similar to A) an automobile battery. B) an electric generator. C) a radio receiver. D) None of the above choices are correct.

an electric generator.

When a bar magnet is broken in two, each half is A) at most half as strong as the original magnet. B) as magnetic as the original magnet. C) actually stronger than the original magnet. D) no longer magnetic.

at most half as strong as the original magnet.

The output power of an ideal transformer is A) smaller than the input power. B) greater than the input power. C) equal to the input power. D) may be any of these

equal to the input power.

Compared to the huge force that attracts an iron tack to a strong magnet, the force that the tack exerts on the magnet is A) relatively small. B) equally huge. C) More information is needed.

equally huge

Superconducting electromagnets A) may be possible in the distant future. B) may be possible in the near future. C) exist now. D) are science fiction.

exist now.

If a compass is moved from the northern hemisphere to the southern hemisphere, its magnetic needle will change direction A) by 90 degrees. B) by 180 degrees. C) depending on where the measurement is taken. D) hardly at all. E) none of these

hardly at all.

Power is transmitted at high voltages because the corresponding current in the wires is A) low so that overheating of the wires is minimized. B) also high to deliver appreciable power to distant places. C) Choices A and B are both true. D) Choices A and B are both false..

low so that overheating of the wires is minimized.

Pigeons navigate primarily by A) a keen sense of smell. B) a good memory. C) magnetic sensors in their heads. D) ultra-high-pitched sounds. E) none of these

magnetic sensors in their heads. D

Which pole of a compass needle points to a south pole of a magnet? A) south pole B) north pole C) both of these

north pole

Magnetic compasses apparently were first used by A) Columbus. B) Vikings. C) Australian aborigines. D) Greeks. E) pigeons, then Chinese.

pigeons, then Chinese.

The intensity of cosmic rays bombarding the Earth's surface is largest at the A) mid-latitudes. B) poles. C) equator.

poles.

Electric power can be transmitted from one place to another without the need for connecting wires in between. This statement is A) sometimes true. B) always false. C) always true.

sometimes true

The primary of a transformer is the coil connected to A) the Internet. B) the power line. C) the load. D) none of these

the power line.

Disconnect a small-voltage battery from a coil of many loops of wire and a large voltage is produced by A) the resistance of the battery to a change in polarity. B) latent energy in the battery. C) electrons already in the wire. D) the electric field between the battery terminals. E) the sudden collapse in the magnetic field.

the sudden collapse in the magnetic field.

A transformer actually transforms A) generators into motors. B) voltage. C) magnetic field lines. D) non-safe forms of energy to safe forms of energy. E) All of the above choices are correct.

voltage