Physics Chapter 6

Direct electric current cannot be used to operate

transformers

Two 240-watt light bulbs are connected in parallel across a 120-V power line. The current in each bulb is A) 1.0 A B) 2.0A C) 0.5 A D) 4.0 A

B) 2.0 A

A magnetic field does not interact with a A) stationary magnet B)stationary electric charge C)a moving magnet D) moving electric charge

B) stationary electric charge

The conventional unit of battery capacity is the ampere-hour, which is actually a unit of A) power B)electric charge C)energy D)potential difference

B)electric charge

At different places on the earth's surface, the earth's magnetic field A) may be different in magnitude but not in direction B)may be different in both magnitude and direction C)may be different in direction but not in magnitude D)is the same in direction and magnitude

B)may be different in both magnitude and direction

Relative to the electric force between two protons, the gravitational force between them is A) any of the choices, depending on how far apart the protons are B)stronger C)weaker D)equal in magnitude

C)weaker

The primary coil of a transformer has 200 turns and its secondary coil has 50 turns, and the current in the secondary coil is 40 A. When a 12-V alternating current is applied to the primary coil of the transformer, the secondary voltage will be

3 V

the current with which a transformer is used A. must be dc. B. must be ac. C. may be either dc or ac. D. may be neither dc nor ac.

must be ac

A current-carrying loop in a magnetic field always tends to turn until the plane of the loop is

parallel to the field

A positive electric charge

repels other positive charges

An atom consists of a

small positive nucleus surrounded at a distance by electrons

When a rubber rod is stroked with a piece of fur,

the rod becomes negatively charged and the fur becomes positively charged

Two charges of +Q are 1 cm apart. If one of the charges is replaced by a charge of -Q, the magnitude of the force between them is

the same

the watt , the unit of power, is equal to the A. (volt)(ampere). B. volt/ampere. C. ampere/volt. D. (volt)(ohm).

(volt)(ampere)

The voltage needed to produce a current of 8 A in a resistance of 12 ohms is

96 V

A charge of +Q attracts a charge of -Q 1 cm away with a force of F. Another charge of +Q is placed next to the first one. The force on the charge of -Q is now A)2F B)4F C)F D)F/2

A)2F

The primary coil of a transformer has 200 turns and its secondary coil has 40 turns. If the current in the secondary coil is 25 A, the current in the primary coil is A)5A B)125 A C)2.5 A D)6.4 A

A)5A

The particle easiest to remove from an atom is an A) neutron B)proton C)nucleus D)electron

D)electron

Superconductors

have no electrical resistance

Protons and electrons have different masses. When they are the same distance apart, the electric force between two electrons

is the same as the force between two protons