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AC Zap

Total questions: 98

Worksheet time: 1hrs 26mins

Name
Class
Date
1.

An oscilloscope shows the current flow above what type of current is it showing?

a)

DC

b)

AC

c)

Rectified Current

d)

Non rectified current

2.
a)

DC

b)

AC

c)

rectified current

d)

non rectified current

3.

A transform has 2400 turns on a primary coil and 120 turns on a secondary coil, the input voltage is 240 volts what is the output voltage?

Secondary voltage / Primary voltage = No. of turns in Secondary coil / No. of turns in Primary coil.

a)

6v

b)

9v

c)

12v

d)

24v

4.

A transform has 14400 turns on a primary coil and 360 turns on a secondary coil, the output voltage is 6 volts what is the input voltage?

Secondary voltage / Primary voltage = No. of turns in Secondary coil / No. of turns in Primary coil.

a)

90

b)

120v

c)

180v

d)

240v

5.

The above half wave form is created by an AC going into which circuit?

a)

single diode

b)

Bridge rectifier

c)

Transformer

d)

Voltage regulator

6.

The above half wave form is created by an AC going into which circuit?

a)

single diode

b)

Bridge rectifier

c)

Transformer

d)

Voltage regulator

7.

What electrical component is used to smooth half wave current signals?

a)

Resistor

b)

Diode

c)

Capacitor

d)

Voltage regulator

8.

What form does an inductor store electricity?

a)

Watts

b)

Joules

c)

Voltage

d)

Current

9.

Why is a voltage regulator used in a power supply circuit?

a)

It can maintain a smooth DC voltage when the circuit is under a load.

b)

It creates a voltage loss.

c)

Voltage regulator are often used with a heat sink that looks cool.

d)

Because it is better to regulate voltage.

10.

What circuits where used to create the wave form pictured?

a)

Single diode and capacitor

b)

Transformer and voltage regulator

c)

Bridge rectifier and smoothing capacitors

d)

Diodes, transistors, resistor and inductors.

11.

In a parallel plate capacitor with air between the plates, each plate has an area of 6x10−3 6x10^{-3\ }   m2m^2   and the distance between the plates is 3 mm. Calculate the capacitance of the capacitor. If this capacitor is connected to a 100 V supply, what is the charge on each plate of the capacitor?

a)

1,771 x 10−9 C1,771\ x\ 10^{-9\ }C  

b)

7,112 x 10−9 C7,112\ x\ 10^{-9\ }C  

c)

17.71 x 10−12 C17.71\ x\ 10^{-12\ }C  

d)

71,12 C

12.

Three capacitors each of capacitance 9 pF are connected in series.

What is the total capacitance of the combination and the potential difference across each capacitor if the combination is connected to a 120 𝑉 supply?

a)

3μF and 33.3 V3\mu F\ and\ 33.3\ V  

b)

3μF and 40 V3\mu F\ and\ 40\ V  

c)

9μF and 33.3 V9\mu F\ and\ 33.3\ V  

d)

9μF and 40 V9\mu F\ and\ 40\ V  

13.

A 12 𝑝F capacitor is connected to a 50 𝑉 battery. How much electrostatic energy is stored in the capacitor?

a)

1.5 x 10−81.5\ x\ 10^{-8}  

b)

1.5 x 10−7 J1.5\ x\ 10^{-7}\ J  

c)

1.5 x 10−5 J1.5\ x\ 10^{-5}\ J  

d)

1.5 x 10−9 J1.5\ x\ 10^{-9}\ J  

14.

A parallel plate capacitor with air between the plates has a capacitance of 8 pF. What will be the capacitance if the distance between the plates is reduced by half, and the space between them is filled with a substance of dielectric constant 6?

a)

96 pF96\ pF  

b)

100 pF

c)

0.96 pF

d)

0.1 pF

15.

Three capacitors of capacitances 2 pF,3 pF and 4 pF are connected in parallel. what is the total capacitance of the capacitors?

a)

9pF

b)

2pF

c)

1pF

d)

1/9 pF

16.

Direct current is where the electrons move in _____ direction. 

It is produced by ___________________. 

In an _____________ current, the electrons rapidly change ______________. 

____________________ has an alternating current.

The mains voltage is _________ and has a _______________ of 50Hz. 

This means that the ____________ change direction 50 times every _________.

(a)  

17.

A 1.5 kW heater is connected to a domestic supply, which is quoted at 240 V, calculate the peak current in the heater and its resistance

a)

8.8 A, 3.8 ohm

b)

44 A, 1.8 ohm

c)

8 A, 38 ohm

d)

6.3 A, 3.8 ohm

18.

A transformer is being used with an alternating supply of 240 V to power a lamp rated as 12V, 3A. The secondary coil of the transformer has 80 turns, calculate the number of turns and current for the primary coil.

a)

1600 turns

0.15 A

b)

1400 turns

0.15 A

c)

160 turns

15 A

d)

16000 turns

0.015 A

19.

The primary winding of an electric train transformer has 400 turns and the

secondary has 50. If the input voltage is 120V(rms) what is the output voltage?

a)

15 V (rms)

b)

30 V (rms)

c)

60 V (rms)

d)

2.4 V

20.

Using the graph and the equation for alternating current, calculate the value of the current at a time 0.48 s.

a)

-16A

b)

16A

c)

-13A

d)

13A

21.
The period of a wave is
a)
the same as frequency
b)
time required to complete one cycle
c)
expressed in amperes
d)
none of the above
22.
A heater is rated as 230 V, 10 kW. The value 230 V refers to
a)
average voltage
b)
r.m.s voltage
c)
peak voltage
23.
In a series resonant circuit,the impedance of the circuit is
a)
minimum
b)
maximum
c)
zero
24.
The r.m.s value of an alternating current is given by steady (D.C) current which when flowing through a given circuit for a given time produces
a)
the more heat than produced by A.C when flowing through the sam circuit
b)
the less heat than produced by A.C when flowing through the sam circuit
c)
the same heat than produced by A.C when flowing through the sam circuit
25.
In a pure inductive circuit
a)
the current is in phase with voltage
b)
the current lags behind the voltage by 90 degrees
c)
the current leads the voltage by 90 degrees
d)
the current can lead or lag voltage by 90 degrees
26.
In an RLC circuit, power loss can take place in
a)
R
b)
L
c)
C
d)
L and C
27.
Poor power factor
a)
reduces load handling capability of electrical system
b)
results in more power losses in electrical system
c)
results in less power losses in electrical system
d)
overloads the power supply
28.
If a sinusoidal wave has a frequency of 50 Hz with 30 A r.m.s current, which of the following equation represents the wave?
a)
42.42 sin 314.2t
b)
60 sin 25t
c)
30 sin 50t
d)
84.84 sin 25t
29.
In a pure inductive circuit, if the supply frequency is reduced to 1/2, the current will 
a)
be reduced by half
b)
be doubled
c)
be four times as high
d)
be reduced to one fourth
30.
Capacitive reactance is more when
a)
capacitance is less and frequency of supply is less
b)
capacitance is less and frequency of supply is more
c)
capacitance is more and frequency of supply is less
d)
capacitance is more and frequency of supply is more
31.

What does rms current stand for?

a)

Root Mean Square

b)

Random Mean Score

c)

Rapid Motion Sensor

d)

Real-time Measurement System

32.

How is rms current calculated in a circuit?

a)

Irms = (1/T) * ∫(i(t))^2 dt

b)

Irms = sqrt((1/T) * ∫(i(t))^2 dt)

c)

Irms = sqrt((1/T) * ∫(i(t))^3 dt)

d)

Irms = sqrt((1/T) * ∫(i(t)) dt)

33.

Explain the relationship between rms current and peak current.

a)

rms current = peak current + 1

b)

rms current = peak current / √2

c)

rms current = peak current * 2

d)

rms current = peak current - 1

34.

Why is rms current important in electrical circuits?

a)

RMS current is important because it measures the voltage in the circuit

b)

RMS current is used to calculate the frequency of the electrical signal

c)

RMS current is crucial for determining the resistance of a circuit

d)

RMS current is important in electrical circuits because it represents the equivalent DC current that would produce the same heating effect in a resistor.

35.

Calculate the rms current if the peak current is 10A.

a)

7.07 A

b)

5.5 A

c)

10.5 A

d)

8.5 A

36.

In a circuit, if the rms current is 5A, what is the peak current?

a)

8A

b)

6A

c)

7.07A

d)

4A

37.

Define rms current and its significance in AC circuits.

a)

RMS current is the equivalent steady DC current that produces the same heating effect in a resistor as an alternating current does. It is crucial in AC circuits for determining effective heating or power dissipation in resistive components.

b)

RMS current is only relevant in DC circuits

c)

RMS current is the average current in an AC circuit

d)

RMS current is the maximum current in an AC circuit

38.

If the peak current in a circuit is 20A, what is the rms current?

a)

14.14A

b)

10A

c)

16.5A

d)

18A

39.

How does rms current differ from average current?

a)

RMS current is only used in AC circuits, while average current is used in DC circuits.

b)

Average current is measured in volts, while RMS current is measured in amperes.

c)

RMS current is always higher than average current.

d)

RMS current considers both magnitude and direction of the current waveform, while average current only considers the magnitude.

40.

Discuss the importance of rms current in power calculations.

a)

RMS current is important in power calculations to accurately represent the effective current in AC circuits.

b)

RMS current is irrelevant in power calculations

c)

Power calculations do not involve current values

d)

Peak current is more accurate than RMS current in power calculations

41.

If the rms current in a circuit is 8A, what is the peak current?

a)

12A

b)

6A

c)

10A

d)

11.31A

42.

What is the formula to calculate rms current in a circuit?

a)

Irms = Ipeak / √2

b)

Irms = Ipeak + √2

c)

Irms = Ipeak - √2

d)

Irms = Ipeak * √2

43.

Compare rms current with instantaneous current in a circuit.

a)

Instantaneous current is always higher than RMS current in a circuit.

b)

RMS current takes into account the entire waveform over a cycle, providing a more accurate measure of the actual heating effect in a circuit.

c)

Instantaneous current is a more accurate measure of the actual heating effect in a circuit compared to RMS current.

d)

RMS current is only relevant for DC circuits, not AC circuits.

44.

If the rms current is 6A, what is the peak-to-peak current?

a)

3A

b)

9A

c)

12A

d)

15A

45.

Explain the concept of effective current in relation to rms current.

a)

Effective current is the peak current value in an alternating current cycle.

b)

Effective current is the value of direct current that would produce the same heating effect in a resistor as an alternating current. It is calculated as the root mean square (rms) value of the alternating current. Therefore, effective current is directly related to rms current.

c)

Effective current is calculated by multiplying the peak current by a factor of 2.

d)

Effective current is always higher than the rms current.

46.

AC stands for

a)

Air-conditioner

b)

Direct Current

c)

Alternating Current

d)

Alternating Voltage

47.

A sine wave has a peak value of 354 V, What is the RMS value?

a)

250 V

b)

500 V

c)

354 V

d)

200V

48.

The mean value of current for half cycle of an ac is 10π\frac{10}{\pi} A, its peak value is 

a)

0 A

b)

1 A

c)

10 A

d)

5 A

49.

The r.m.s value of an alternating current is given by steady (D.C) current which when flowing through a given circuit for a given time produces

a)

the more heat than produced by A.C when flowing through the sam circuit

b)

the same heat than produced by A.C when flowing through the same circuit

c)

the less heat than produced by A.C when flowing through the sam circuit

50.

What does RMS means?

a)

Really Monday Stinks

b)

Root Minus Square

c)

Root Mean Square

d)

Root Minus Subtraction

51.

An electric current flowing in one direction only

a)

voltage

b)

parallel current

c)

direct current

d)

electric current

52.

apparent value of ac is

a)

mean value for full cycle

b)

mean value for half cycle

c)

rms value

d)

all

53.

Mean value of ac for half cycle is

a)

zero

b)

i02\frac{i_0}{\sqrt{2}}

c)

2i0π\frac{2i_0}{\pi}

d)

None

54.

The electricity in our house is

a)

AC

b)

DC

c)

BC

d)

AD

55.

Battery is

a)

AC source

b)

DC source

c)

none of the above

d)

all of the above

56.

Which one of the below AC parameters show the effective Dc value?

a)

Peak Value

b)

RMS value

c)

Peak to peak value

d)

Frequency

57.
A heater is rated as 230 V, 10 kW. The value 230 V refers to
a)
average voltage
b)
r.m.s voltage
c)
peak voltage
58.

What is the largest (or maximum) instantaneous value in the sine wave?

a)

RMS voltage

b)

Peak voltage

c)

Apparent power

d)

Capacitance

59.

What is the length of time required for one cycle?

a)

Frequency

b)

Period

c)

Resonant frequency

d)

Time constant

60.

Which value is calculated by multiplying the peak value by 0.707?

a)

Peak-to-peak voltage

b)

Effective value (RMS)

c)

Inductive reactance

d)

Impedance

61.

What converts AC power to DC power?

a)

Transformer

b)

Rectifier

c)

Capacitor

d)

Inductor

62.

What is the time required for the voltage across a capacitor to rise to 63.2% of the source voltage?

a)

Period

b)

Time constant

c)

Cycle

d)

Power factor

63.

What is the maximum difference between the positive peak and the negative peak voltage?

a)

Peak-to-peak voltage

b)

True power

c)

Sine wave

d)

Dielectric

64.

What is the basis of all transformer operations, where one inductor's magnetic flux affects another?

a)

Resonance

b)

Mutual induction

65.

What is one half cycle of an AC waveform called?

a)

Cycle

b)

Alternation

c)

Period

d)

Sine wave

66.

What type of AC waveform is produced by a rotary generator?

a)

Square wave

b)

Sawtooth wave

c)

Sine wave

d)

Triangular wave

67.

What is the ratio of True Power to Apparent Power?

a)

Power factor

b)

Impedance

c)

Phase angle

d)

Capacitive reactance

68.

What is the number of cycles per second called?

a)

Period

b)

Resonant frequency

c)

Frequency

d)

Time constant

69.

What type of current changes direction and magnitude at regular intervals?

a)

Direct current (DC)

b)

Alternating current (AC)

c)

Reactive current

d)

Inductive current

70.

What value is also known as RMS and produces the same amount of heat as a corresponding amount of DC?

a)

Peak value

b)

True power

c)

Effective value (RMS)

d)

Apparent power

71.

What is the unit of measure for an Inductor?

a)

Farad

b)

Henry

c)

Ohm

72.

What is the unit of measure for a Capacitor?

a)

Henry

b)

Farad

c)

Ohm

d)

Watt

73.

What term describes when voltage or current passes through a series of changes, returns to the starting point, and then again starts the same series of changes?

a)

Alternation

b)

Cycle

c)

Resonance

d)

Period

74.

Which law states that the voltage induced into a conductor is of such a polarity that it opposes the change that caused it?

a)

Ohm's Law

b)

Kirchhoff's Law

c)

Lenz's Law

d)

Faraday's Law

75.

What is known as non-conductive material?

a)

Conductor

b)

Dielectric

c)

Resistor

d)

Inductor

76.

What is the combined effect of resistance, inductive reactance, and capacitive reactance?

a)

Impedance

b)

Capacitance

c)

Reactance

d)

Conductance

77.

What term describes the reactive power of the circuit and the power consumed by the entire circuit?

a)

True power

b)

Apparent power

c)

Effective power

d)

Peak power

78.

What is the frequency at which the inductive reactance is equal to the capacitive reactance?

a)

Resonant frequency

b)

Power factor

c)

Time constant

d)

Period

79.

What is the opposition that a capacitor presents to the flow of Alternating Current?

a)

Inductance

b)

Capacitance

c)

Capacitive reactance

d)

Impedance

80.

What is the opposition that an inductor presents to the flow of Alternating Current?

a)

Resistance

b)

Inductance

c)

Capacitance

d)

Impedance

81.

Which of the following terms is related to the ability of a component to store electrical energy in an electric field?

a)

Capacitance

b)

Inductance

c)

Capacitive reactance

d)

Inductive reactance

82.

The opposition to AC current flow presented by capacitors and inductors is called:

a)

Resistance

b)

Reactance

c)

Impedance

d)

Reluctance

83.

A resistor is connected to an AC power supply. The current in this circuit ____

a)

Leads the voltage by 90

b)

Lags the voltage by 45°

c)

Lags the voltage by 90°

d)

in phase with the voltage

84.

In an AC series circuit, the current in a pure resistor differs in phase with the applied voltage by what angle?

a)

0°

b)

45°

c)

90°

d)

80°

85.

The voltage output of an AC source is given by the expression ∆v = 200 sin wt, where ∆v is in volts. What is the rms current in the circuit when this source is connected to a 100 ohms resistor.

a)

300 A

b)

2.82 A

c)

2.0 A

d)

1.41 A

86.

Which of the following statements can be true for a resistor connected in a simple series circuit to an operating AC generator?

I. The average power dissipated in the resistor is positive

II. The average power dissipated in the resistor is zero

III. The average current is zero

a)

I only

b)

II only

c)

III only

d)

I and III only

87.

In an AC series circuit, the current in a pure capacitor differs in phase with the applied voltage by what angle

a)

0°

b)

45°

c)

90°

d)

180°

88.

The graph below represents an AC circuit that consists of a generator and a capacitor. The voltage __________.

a)

lags the current by 45°

b)

lags the current by 90°

c)

leads the current by 45°

d)

leads the current by 90°

89.

As the frequency of the AC voltage across a capacitor approaches zero, the capacitive reactance of that capacitor _______.

a)

approaches zero

b)

approaches infinity

c)

becomes negative

d)

does not change

90.

Which of the following statements about capacitive reactance is true?

a)

It is independent of capacitance

b)

It is very small at low frequencies

c)

decreases with increasing capacitance

d)

increases with increasing capacitance

91.

The graph below represents an AC circuit that consists of a generator and an inductor. The voltage __________.

a)

lags the current by 45°

b)

lags the current by 90°

c)

leads the current by 45°

d)

leads the current by 90°

92.

An inductor and a resistor are connected in series across an AC generator, as shown below. Immediately after the switch is closed, which of the following statements is true?

a)

The current in the circuit is ∆V/R

b)

The current in the circuit is zero

c)

The voltage across the inductor is zero

d)

The voltage across the inductor is ∆V/2

93.

The current in an inductor connected to an AC voltage source lags the voltage. The lag is caused by the ____.

a)

back emf in the coil

b)

resistance of the coil

c)

voltage across the coil

d)

frequency of the source

94.

A 30 mH inductor in a circuit carries a current of 0.50 A. When the switch is opened the current decreased to zero in 15 ms. What is the back emf of this inductor?

a)

0.25 V

b)

1.0 V

c)

25 V

d)

250 V

95.

When a particular inductor is connected to a source of sinusoidal varying voltage with constant amplitude and a frequency of 60.0 Hz, the rms current is 3.0 A. What is the rms current if the source frequency is doubled?

a)

1.5A

b)

3.0 A

c)

4.2 A

d)

6.0 A

96.

An emf of 1.0 V is induced in an inductor when the current decreases at a rate of 0.05 A/s. What is the inductance of the inductor?

a)

5 H

b)

10 H

c)

15 H

d)

20 H

97.

Inductive Reactance is actually a consequence of

a)

Gauss's Law

b)

Coulomb's Law

c)

Faraday's Law

d)

Newton's Law

98.

If the frequency of the AC voltage across an INDUCTOR is doubled, the inductive reactance of that inductor ______.

a)

decreases to one-half its original value

b)

increases to twice its original value

c)

decreases to one-fourth its original value

d)

increases to 4 times its original value

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