Download Current and Resistance

Q1) The figure below shows four situations in which positive and
negative charges move horizontally through a region and gives the
rate at which each charge moves. Rank the situations according to
the effective current through the regions, greatest first.
1) a = d , c, b
2) a, d, b, c
3) a = b = c, d
4) all tie
5) none of the above
Q2) In the circuit shown, the current flows counterclockwise
(CCW). This means
1) the electrons flow CCW.
2) the electrons flow CW.
3) the protons flow CCW.
4) the protons flow CW.
Q3) Conduction electrons move to the right in a certain wire. This
indicates that:
1) the current density and electric field both point right
2) the current density and electric field both point left
3) the current density points right and the electric field points left
4) the current density points left and the electric field points right
5) the current density points left but the direction of the electric
field is unknown
Q4) A copper cylinder is machined to have the following shape.
The ends are connected to a battery so that a current flows through
the copper. Which region A, B, or C has the greatest magnitude
current density J?
1) A
2) B
3) C
4) all three have the same J.
A
B
C
Q5) The figure below shows conduction electrons moving leftward
through a wire. Are the following leftward or rightward: (a) the
current i, (b) the current density J , (c) the electric field E in the
wire
1) (a) rightward
2) (a) rightward
3) (a) rightward
4) (a) leftward
5) (a) leftward
(b) rightward
(b) leftward
(b) leftward
(b) leftward
(b) rightward
(c) rightward
(c) rightward
(c) leftward
(c) leftward
(c) leftward
Q6) For an ohmic substance, the electron drift velocity is
proportional to:
1) the cross-sectional area of the sample
2) the length of the sample
3) the mass of an electron
4) the electric field in the sample
5) none of the above
Q7) The voltage across the ends of a wire is doubled. Which one of
the following statements concerning the resistance of the wire is
true?
1) The resistance is decreases by a factor of four.
2) The resistance is decreases by a factor of two.
3) The resistance is not changed.
4) The resistance increases by a factor of two.
5) The resistance increases by a factor of four.
Q8) A copper cylinder is machined to have the following shape.
The ends are connected to a battery so that a current flows through
the copper. Which region A, B, or C has the greatest magnitude
electric field E?
1) A
2) B
3) C
4) all three have the same E.
A
B
C
Q9) Two cylindrical resistors are made of the same material (same
resistivity ). Resistor 2 is twice as long and has twice the
diameter of resistor 1. What is the ratio
1) 2
2) 4
3) 1/2
4) 1/4
5) 1
R2
?
R1
1
2
Q10) A certain wire has resistance R. Another wire, of
the same material, has half the length and half the
diameter of the first wire. The resistance of the second
wire is:
1) R/4
2) R/2
3) R
4) 2R
5) 4R
Q11) Two cylindrical copper wires have the same mass.
Wire A is twice as long as wire B. Their resistances are
related by
1) RA = RB
2) RA = 2RB
3) RA = 4RB
4) RA = 8RB
Q12) You apply a potential difference V to a wire-resistor, causing
a current to flow through the resistor. Next, the resistor is removed
from the circuit and the wire in it is cut in half lengthwise. One of
the halves is placed back into the circuit, with the same potential
difference V applied to it. How does the current through the new
resistor compare to the old?
1) it is larger than the old current
2) it is smaller than the old current
3) it is the same as the old current
Q13) A cylindrical copper rod has resistance R. It is reformed to
twice its original length with no change of volume. Its new
resistance is:
1) R
2) 2R
3) 4R
4) 8R
5) R/2
Q14) Which one of the following statements concerning resistance
is true?
1) The resistance of a semiconductor increases with temperature.
2) Resistance is a property of resistors, but not conductors.
3) The resistance of a metal wire changes with temperature.
4) The resistance is the same for all samples of the same material.
5) The resistance of a wire is inversely proportional to the length of
the wire.
Q15) Will the current in an ordinary light bulb be greater
immediately after it is turned on or a few minutes later?
1) immediately after it is turned on
2) a few minutes later
3) the current will be the same
Q16) Which of the following graphs best represents the
current-voltage relationship of an incandescent light bulb?
1) I
2) II
3) III
4) IV
5) V
Q17) The current is zero in a conductor when no potential
difference is applied because:
1) the electrons are not moving
2) the electrons are not moving fast enough
3) for every electron with a given velocity there is another with a
velocity of equal magnitude and opposite direction.
4) equal numbers of electrons and protons are moving together
5) otherwise Ohm's law would not be valid
Q18) The potential difference across the ends of a wire is doubled
in magnitude. If Ohm's law is obeyed, which one of the following
statements concerning the resistance of the wire is true?
1) The resistance is one half of its original value.
2) The resistance is twice its original value.
3) The resistance is not changed.
4) The resistance increases by a factor of four.
5) The resistance decreases by a factor of four.
Q19) What is the effect on the current in a wire if the voltage
across the wire is doubled and the resistance is cut in half?
1) the current decreases by a factor of four
2) the current decreases by a factor of two
3) the current stays the same
4) the current increases by a factor of two
5) the current increases by a factor of four
Q20) The figure below shows three cylindrical copper conductors
along with their face areas and lengths. Rank them according to the
current through them, greatest first, when the same potential
difference V is placed across their lengths
1) a & c tie, b
2) b, a & c tie
3) all tie
4) a, c, b
5) b, a, c
Q21) You wish to double the rate of energy dissipation in a heating
device. You could:
1) double the potential difference keeping the resistance the same
2) double the current keeping the resistance the same
3) double the resistance keeping the potential difference the same
4) double the resistance keeping the current the same
5) double both the potential difference and the current
Q22) The current through a certain heater wire is found to be fairly
independent of its temperature. If the current through the heater
wire is doubled, the amount of energy delivered by the heater in a
given time interval will
1) increase by a factor of two.
2) decrease by a factor of two.
3) increase by a factor of four.
4) decrease by a factor of four.
5) increase by a factor of eight.
Q23) A potential difference V is connected across a device with resistance
R, causing current I through the device. Rank the following variations
according to the change in the power, greatest change first:
(a) V is doubled with R unchanged, (b) I is doubled with R unchanged,
(c) R is doubled with V unchanged, (d) R is doubles with I unchanged
1) all tie
2) a and b tie, d, c
3) c, d, a and b tie
4) a and b tie, c and d tie
5) c and d tie, a and b tie
Q24) Three wires, of the same diameter, are connected in turn between
two points maintained at a constant potential difference. Their resistivities
and lengths are  and L (wire A), 1.2 and 1.2L (wire B), and 0.9 and L
(wire C). Rank the wires according to the rate at which energy is
transferred to thermal energy within them, greatest first.
1) A, B, C
2) A, C, B
3) B, C, A
4) B, A, C
5) none of the above
Q25) Two light bulbs are in series attached to a battery as shown.
The bulbs are marked 40W and 60W. Which bulb is brighter?
1) both have same brightness
2) 40W is brighter
3) 60W is brighter
V
40W
60W
Q26) A flat iron is marked “120V, 600W". In normal use, the
current in it is:
1) 2A
2) 4A
3) 5A
4) 7.2A
5) 0.2A
Q27) The ampere-hour is used to rate batteries. What quantity
does this measure?
1) current
2) charge
3) resistance
4) energy
5) work