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