Voltage, Current and Resistance exam
This exam will be divided into two parts, the first is multiple choice worth 4 points each. Following that there will be problems that need to be worked out, remember to show work to gain partial credit.
Multiple choice please circle the best alternative that completes the statement or answers the question.
1) The resistance of a wire can be written as
a) (Current)*(Voltage)
b) (Voltage)/(Current)
c) (Current)/(Voltage)
d) None of the given answers
2) What is one (1) Watt equivalent to?
a) 1 W*A
b) 1 V/W
c) 1 V*A
d) 1 A/V
3) If the voltage across a circuit of constant resistance is doubled the power dissipated by that circuit will
a) Decrease to one fourth
b) Decrease to one half
c) Double
d) Quadruple
4) During a power demand, the voltage output is reduced by 5.0%. By what percentage is the power on a resistor affected?
a) 2.5% less
b) 90% less
c) 5.0% less
d) 10.0% less
5) A 200 W resistor is rated at ¼ W. What is the maximum current it can draw?
a) 0.35 A
b) 0.035 A
c) 0.25 A
d) 0.50 A
6) How much does it cost to operate a 25-Watt soldering iron for 8.0 hours, if energy costs $0.08/kWh?
a) $0.016
b) $0.25
c) $1.50
d) $0.16
7) When two or more resistors are connected in series to a battery
a) The equivalent resistance of the combination is equal to the sum of the resistances of each resistor.
b) The same current flows through each resistor
c) The total voltage across the combination is the algebraic sum of the voltage across the individual resistors
d) All the given answers
8) You obtain a 100-Watt light bulb and a 50-Watt light bulb. Instead of connecting them in the normal way, you devise a circuit that places them in series across normal household voltage. Which statement is correct?
a) The 100-Watt bulb glows brighter than the 50-Watt bulb.
b) Both bulbs glow at the same increased brightness.
c) The 50-Watt bulb glows more brightly than the 100-Watt bulb.
d) Both bulbs glow at the same reduced brightness.
9) When resistors are connected in parallel, we can be certain that
a) The same current flows in each one
b) The potential difference across each is the same
c) Their equivalent resistance is greater than the resistance of any one of the individual resistances.
d) The power dissipated in each is the same.
10) The lamps in a string of Christmas tree lights are connected in parallel. What happens if one lamp burns out? (Assume negligible resistance in the wires)
a)The brightness of the lamps will not change much at all.
b) The other lamps get dimmer, but some dimmer than others
c) The other lamps get brighter equally
d) The other lamps get dimmer equally
11) Three identical capacitors are connected in series to a battery. If a total charge of Q flowed from the battery, how much charge does each capacitor hold?
a) 3Q
b) Q/9
c) Q/3
d) Q
12) An ideal ammeter should
a) introduce very large series resistance into the circuit whose current is to be measured.
b) have a high coil resistance.
c) Introduce a very small series resistance into the circuit whose current is to be measured.
d) consist of a galvanometer in series with a large resistor.
13) A resistor and a capacitor are connected in series to an ideal battery of constant terminal voltage. At the moment contact is made with the battery, the voltage across the capacitor is
a) Equal to the battery’s terminal voltage
b) Zero
c) Greater than the battery’s terminal voltage
d) Less than the battery’s terminal voltage, but greater than zero
14) A resistor and a capacitor are connected in series to an ideal battery of constant terminal voltage. At the moment contact is made with the battery, the voltage across the resistor is
a) less than the battery’s terminal voltage, but greater than zero.
b) equal to the battery’s terminal voltage
c) greater than the battery’s terminal voltage.
d) zero.
Problems. Show all work to obtain maximum partial credit.
15) How many joules of energy are stored in a 12-Volt car battery rated at 100 Amp hours when it is fully charged?
16) Three resistors of size 1, 2, and 3 ohms respectively are connected in series to a 12 Volt battery. What is the power dissipated in each resistor?
17) Determine the equivalent resistance between points x and y in the figure. Assume each resistor is identical and has a value R.
X Y