Electricity Flashcards
An accidental path of low resistance bypassing the intended path and allowing passage of an abnormally high amount of current is known as what?
Short circuit
How may the unit “hertz” be best described?
(a) revolutions per minute
(b) cycles per second
(c) coulombs per second
(d) revolutions per second
(b) cycles per second
In a series circuit what is the total applied voltage equal to?
(a) the total current divided by the total resistance
(b) the sum of the individual currents multiplied by the number of resistors
(c) the total resistance divided by the total current
(d) the sum of the individual voltage drops
(d) the sum of the individual voltage drops
[In a series circuit, Et = E1 + E2 + E3…]
In a series circuit, which value will remain unchanged at all places in the circuit?
(a) Inductance
(b) Voltage
(c) Current
(d) Resistance
(c) Current
[In a series circuit, It = I1 = I2 = I3…]
Four lamps are connected in series in a single circuit. If one of the lamp burns out, what will happen to the other lamps?
(a) become brighter
(b) become dimmer
(c) burn with their original intensities
(d) all go out
(d) all go out
[In a series circuit, a burned out light bulb creates an open circuit, ie. no current flow though the circuit.]
Which of the following statements concerning a circuit with parallel connected resistors is correct?
(a) The voltage drop across each resistor is the same.
(b) The total current flow equals the reciprocal of the sum of the individual currents.
(c) The total voltage equals the sum of the individual voltages across each resistance.
(d) The total resistance equals the sum of the individual resistances.
(a) The voltage drop across each resistor is the same.
[In a parallel circuit, Et = E1 = E2 = E3…]
Which of the following statements is true concerning circuits with parallel connected resistances?
(a) The total current flow equals the sum of the individual currents.
(b) The total voltage equals the sum of the individual voltages across each resistance.
(c) The total current flow equals the reciprocal of the sum of the individual currents.
(d) The total resistance equals the sum of the individual resistance.
(a) The total current flow equals the sum of the individual currents.
[In a parallel circuit, It = I1 + 12 = I3…]
What statement is true concerning the total resistance of a parallel circuit?
(a) The total resistance is equal to the sum of the individual branch resistances divided by the number of branches.
(b) The total resistance is larger than that of the branch with the greatest resistance.
(c) The total resistance is smaller than that of the branch with the lowest resistance.
(d) The total resistance is equal to the sum of the individual branch resistances.
(c) The total resistance is smaller than that of the branch with the lowest resistance.
[In a parallel circuit, 1/Rt = 1/R1 + 1/R2 + 1/R3…]
Four lamps are connected in parallel in a single circuit. If one of the lamp burns out, what will happen to the other lamps?
(a) become brighter
(b) all go out
(c) burn with their original intensities
(d) become dimmer
(c) burn with their original intensities
[In a parallel circuit, if one branch of the circuit goes out, current will still flow through the remaining branches with the same circuit voltage.]
Which statement is true concerning the total power consumed in a parallel circuit?
(a) The total power is always less than the power consumed by the smallest load.
(b) The total power is equal to the sum of the powers consumed by each individual load.
(c) The total power is never more than the power consumed by the largest load.
(d) The total power is the sum of the powers consumed by each load (resistor) divided by the
number of loads.
(b) The total power is equal to the sum of the powers consumed by each individual load.
Which of the electrical properties listed will always be the same across each component in a parallel circuit?
(a) Voltage
(b) Resistance
(c) Current
(d) Impedance
(a) Voltage
[In a parallel circuit, Et = E1 + E2 = E3…]
What will happen to the total circuit resistance when additional parallel circuits are added to a circuit?
(a) it will increase, causing a decrease in the line voltage
(b) it will decrease, causing an increase in the line voltage
(c) it will increase, causing a drop in the total load current
(d) it will decrease, causing an increase in the total load current
(d) it will decrease, causing an increase in the total load current
In a simple DC circuit, the resistance is held constant while the applied voltage is halved. What will be the effect on the current flow as compared to the original current?
(a) be divided by four
(b) remain the same
(c) be divided by two
(d) double
(c) be divided by two
Example:
If R=6 and E=3, then I=0.5
If R=6 and E=1.5, then I=0.25
A 125 volt DC motor is rated at 10 kW. What is the current rating of the motor?
(a) 4.6 amps
(b) 8.0 amps
(c) 46.2 amps
(d) 80 amps
(d) 80 amps
I = P / E I = 10kW / 125v I = 10000 / 125
If a circuit has resistances of 5, 10, and 20 ohms connected in parallel, what is the combined total resistance of the circuit?
(a) 1.5 ohms
(b) 2.9 ohms
(c) 17.5 ohms
(d) 35.0 ohms
(b) 2.9 ohms
1/Rt = 1/R1 + 1/R2 + 1/R3 1/Rt = 1/5 + 1/10 + 1/20 1/Rt = 0.35 Rt = 2.9
Which of the following statements is correct for the illustrated circuit in figure “B”? Illustration EL-0020
(a) ‘R1’, ‘R2’, and ‘R3’ are connected in series.
(b) The total resistance equals 1/R1 + 1/R2 + 1/R3.
(c) ‘R1’, ‘R2’, and ‘R3’ are connected in parallel.
(d) The voltages measured across ‘R1’, ‘R2’, and ‘R3’ are equal.
(a) ‘R1’, ‘R2’, and ‘R3’ are connected in series.
Referring to figure “B” of the illustration, what statement is true? (EL-0020)
(a) The current drawn by the circuit will be inversely proportional to the total resistance of the entire circuit.
(b) If the resistance values of the individual resistors are uniquely different, each resistor will have a uniquely different current draw.
(c) The current drawn by the circuit will be directly proportional to the total resistance of the entire circuit.
(d) The current drawn by an individual resistor will be proportional to the resistance of that resistor.
(a) The current drawn by the circuit will be inversely proportional to the total resistance of the entire circuit.
[If resistance increases, current will decrease. If resistance decreases, current will increase.]
Referring to figure “B” of the illustration, what statement is true? (EL-0020)
(a) The order of resistors connected in the series string has no impact on the total resistance. The total resistance of the circuit will be less than any one of the individual resistances.
(b) The order of resistors connected in the series string has an impact on the total resistance. If the largest resistance is last in the circuit, the total resistance will be more than if it is not.
(c) The order of resistors connected in the series string has no impact on the total resistance. The sum of the resistances is the total resistance of the circuit.
(d) The order of resistors connected in the series string has an impact on the total resistance. If the largest resistance is first in the circuit, the total resistance will be more than if it is not.
(c) The order of resistors connected in the series string has no impact on the total resistance. The sum of the resistances is the total resistance of the circuit.
[In a series circuit, Rt = the sum of all resistors, regardless of the resistor order.]
What statement is true concerning the electrical diagram shown in figure “B” of the illustration? EL-0019
(a) The voltages measured across ‘R1’, ‘R2’ and ‘R3’ will be different if ‘R1’, ‘R2’ and ‘R3’ have different values.
(b) The total resistance equals R1 + R2 + R3.
(c) ‘R1’, ‘R2’, and ‘R3’ are connected in parallel.
(d) ‘R1’, ‘R2’, and ‘R3’ are connected is series.
(c) ‘R1’, ‘R2’, and ‘R3’ are connected in parallel.
As shown in figure “A” of the illustration, with the switch closed what statement is true if ‘R1’ and ‘R2’ have unequal resistance values? EL-0019
(a) The energy dissipated in ‘R1’ will be the same as the energy dissipated in ‘R2’.
(b) The voltage drop across ‘R1’ will not be equal to the voltage drop across ‘R2’.
(c) The current flow through ‘R1’ will equal the current flow through ‘R2’.
(d) The current flow through ‘R1’ will differ from the current flow through ‘R2’.
(d) The current flow through ‘R1’ will differ from the current flow through ‘R2’.
[In a parallel circuit, current flow through each branch is inversely proportional to the resistance across each branch.]
What is the total resistance of figure “B” of the illustrated circuit if the resistance of R1 is 3 ohms, R2 is 4 ohms, and R3 is 5 ohms? EL-0020
(a) 0.5 ohms
(b) 1.28 ohms
(c) 1.5 ohms
(d) 12 ohms
(d) 12 ohms
In a series circuit, Rt = R1 + R2 + R3
Rt = 3 + 4 + 5
Rt = 12 ohms
What is the total resistance of the electrical circuit illustrated in figure “B” if the resistance of R1 is 2 ohms, R2 is 4 ohms, and R3 is 4 ohms and the battery voltage is 6 volts? EL-0019
(a) 0.01 ohms
(b) 0.10 ohms
(c) 1.00 ohms
(d) 10.00 ohms
(c) 1.00 ohms
In a parallel circuit, 1/Rt = 1/R1 + 1/R2 + 1/R3
1/Rt = 1/2 + 1/4 + 1/4
1/Rt = 1 ohm
What will be the total current in figure “B” of the illustrated circuit with the switch closed if the applied voltage is 24 volts and the resistance of R1 is 3 ohms, R2 is 4 ohms, and R3 is 5 ohms, respectively? EL-0020
(a) 2 amps
(b) 6 amps
(c) 8 amps
(d) 10 amps
(a) 2 amps
I = E / R
In a series circuit, Rt = R1 + R2 + R3
Rt = 3 + 4 + 5 = 12 ohms
I = 24v / 12ohms
In figure “A” of the illustration, 12 volts is applied to the circuit where the resistance of R1 is 10 ohms and R2 is 10 ohms. what is the voltage across R2 when the switch is closed? EL-0020
(a) 1.2 volts
(b) 2 volts
(c) 6 volts
(d) 12 volts
(c) 6 volts
In a series circuit, Et = E1 + E2 and is proportional to their individual resistances.
Because R1 = R2, they split the voltage equally.
12v / 2 = 6v