Here you can get the Physics Chapter 16 Alternating Current MCQs 2nd Year for the Entry Test preparations. The current which is produced by a voltage source whose polarity keeps on reversing is called Alternating Current. There are many AC circuits used to supply Alternating current. In a capacitor, direct current cannot flow. So alternating current is used in the capacitors. The study of AC in an inductor is quite important. The term impedance is used to show the combined effect of resistance and reactance. There are R-C and R-L series circuits. Electromagnetic waves require no medium for their propagation. A term called modulation is used to combine low-frequency signal with the high-frequency radio wave. So, this is a short introduction to this chapter. Have a look at the important MCQs of this chapter below.

## Physics Chapter 16 Alternating Current MCQs 2nd Year

**KEY POINTS**

- Alternating Current
- C circuits
- C through a Resistor
- C through a capacitor
- C through an inductor
- Impedance
- R-C and R-L series circuits
- Series Resonance circuit
- Parallel Resonance circuit
- Principle of Metal Detectors
- Electromagnetic waves
- Modulation

**Question#01: A Choke is used as resistance in ______.**

- DC circuit
- AC circuit
- Both AC and DC
- Full-wave rectifier circuit

### Answer

### Answer

**AC circuit**

**Question#02: At resonance, the value of the power factor in an L-C-R series circuit is________.**

- Zero
- 1/2
- 1
- non-definite

### Answer

### Answer

**1**

**Question#03: An AC series circuit contains 4ohm resistance and 3ohm inductive resistance. The impedance of the circuit is______.**

- 1ohm
- 5ohm
- 7ohm
- 7/2 ohm

### Answer

### Answer

**5ohm**

**Question#04: An inductive coil has a resistance of 100ohm. When an AC signal of frequency 1000Hz is fed to the coil, the applied voltage leads the current by 45 degrees. What is the inductance of the coil?**

- 10mH
- 12mH
- 16mH
- 20mH

### Answer

### Answer

**16mH**

**Question#05: Choose the correct statement. In the case of AC circuit, ohm’s law hold for ________.**

- Peak values of Voltage and current
- The effective value of voltage and current
- Instantaneous values of voltage and current
- All of the above

### Answer

### Answer

**All of the above**

**Question#06: The phase angle between the voltage and the current in an AC circuit consisting of a resistance______.**

- Zero
- 45degree
- 90degree
- 180 degree

### Answer

### Answer

**Zero**

**Question#07: In an LCR series circuit, if V is the effective value of the applied voltage, V _{R} is the voltage across R, V_{L} is the effective voltage across L and V_{C} is the effective voltage across C then_________.**

- V=V
_{R}+V_{L}+V_{C} - V
^{2}=V_{R}^{2}+V_{L}^{2}+V_{C}^{2} - V
^{2}=V_{R}^{2}+(V_{L}-V_{C})^{2} - V
^{2}=V_{L}^{2}+(V_{R}-V_{C})^{2}

### Answer

### Answer

**V**

^{2}=V_{R}^{2}+(V_{L}-V_{C})^{2}**Question#08: When a voltage V=V coswt is applied across a resistor of resistance R, the average power dissipated per cycle in the resistor is given by______.**

- V
_{o}/**√**2R - V
_{o}/√2wR - V
_{o}^{2}/ 2R - V
_{o}^{2}/2wR

### Answer

### Answer

**V**

_{o}^{2}/2wR**Question#09: Two identical coaxial circular loops carry equal currents in the same direction. If the loops approach each other, the current in__________.**

- Each increase
- Each Decrease
- Each remains constant
- One increases whereas that in the other decreases

### Answer

### Answer

**Each increase**

**Question#10: An inductor may store energy in________.**

- Its electric field
- It’s coils
- Its magnetic field
- both electrical and magnetic

### Answer

### Answer

**Its magnetic field**

**Question#11: Average value of current and voltage over a cycle of AC is**

- Positive
- Negative
- both
- zero

### Answer

### Answer

**both**

**Question#12: A changing magnetic flux produces around itself an induced ________.**

- Magnetic field
- Electrical Field
- Electromagnetic force
- Artificial Gravitational Field

### Answer

### Answer

**Electrical Field**

**Question#13: Maxwell derived mathematically that the velocity of the electromagnetic waves is________.**

- 1/E
_{o} - 1/ √µo/Eo
- √µo Eo
- 1/√µo Eo

### Answer

### Answer

**1/√µo Eo**

**Question#14: Electromagnetic waves travel in the free space with the speed of______.**

- Gama-rays
- Positive rays
- Cathode rays
- Beta-rays

### Answer

### Answer

**Gama-rays**

**Question#15: The direction of propagation of an electromagnetic waves is______.**

- The perpendicular to the electric field
- the perpendicular to the electric and magnetic field
- perpendicular to the magnetic field
- Parallel to the electric and magnetic field

### Answer

### Answer

**the perpendicular to the electric and magnetic field**

**Question#16: An electromagnetic waves consists of_____.**

- Electric and magnetic fields moving parallel to each other
- Magnetic field moving with velocity of light in space
- Electric field moving with velocity of light
- Electric and magnetic fields moving perpendicular to each other

### Answer

### Answer

**Electric field moving with velocity of light**

**Question#17: Electromagnetic waves transport_______.**

- Energy
- Mass
- Heat
- None

### Answer

### Answer

**None**

**Question#18: Waves emitted from the antenna are______.**

- Sound waves
- Electromagnetic waves
- Radio Waves
- Modulated waves

### Answer

### Answer

**Electromagnetic waves**

**Question#19: A choke coil has**

- High Inductance and high resistance
- High inductance and low resistance
- Low inductance and high resistance
- Low inductance and high resistance

### Answer

### Answer

**High inductance and low resistance**

**Question#20: Natural or Resonant frequency of an LC circuit is______.**

- 1/4π
**√**LC - 2π√LC
- 1/√LC
- 1/ 2π

### Answer

### Answer

**1/ 2π**

**Question#21: If capacitance of L-C circuit is made four rimes then frequency of the ciircuit becomes_____.**

- Twice
- one half
- Four times
- None

### Answer

### Answer

**None**

**Question#22: A capacitance 30 micro Farad is charged by a constant current of 10mA. If initially the capacitor was uncharged, what is the time taken for the potential difference across the capacitor to reach 300V?**

- 0.9 sec
- 15 sec
- 1.5 x 10^5 sec
- 0.9 x 10^-2 sec

### Answer

### Answer

**1.5 x 10^5 sec**

**Question#23: The value of the steady current, which when flowing through the same resistor produces heat at the same rate as the mean rate of heat produced by the alternating current is______.**

- Average current
- Sinusoidal Current
- r.m.s current
- Net current

### Answer

### Answer

**Sinusoidal Current**

**Question#24: To find the r.m.s value of and alternating current mathematically, we need to have_____.**

- Mean value of I
^{2} - Square root of mean value of I
^{2} - Square root of I
^{2} - Square of I/2

### Answer

### Answer

**Square root of I**

^{2}**Question#25: An alternating current of r.m.s value of 4.0 A and frequency 50 Hz flows in a circuit containing 10 ohm resistor. The peak current is then_____.**

- 20A
- 20.66A
- 6.66A
- 5.66A

### Answer

### Answer

**20A**

**Question#26: An alternating Current of r.m.s value of 2A and a steady direct current I flowing through identical resistors dissipate heat at the same rate. What is the current I?**

- 2A
- √2 A
- 1A
- 2√2 A

### Answer

### Answer

**2A**

**Question#27: An A.C current is represented by the equation I=I _{o }sin w t, which of the following equation represents an alternating current of frequency and amplitude twice of the above current?**

- I=2 I
_{o}sin (w t/2) - I=W I
_{o }sin (2wt) - I=2I sinwt
- I=I
_{o }sin(2wt)

### Answer

### Answer

**I=I**

_{o }sin(2wt)** Question#28: In pure resistor circuit, the voltage and current are______.**

- Lagging each other
- They are at 90
^{o}phase difference - They have zero phase difference
- No phase difference

### Answer

### Answer

**Lagging each other**

**Question#29: The power factor of an AC circuit has the value**

- Unity when the circuit contains only an inductance
- Unity when the circuit contains only A resistance
- Unity when the circuit contains only resistance and capacitor
- Unity when the circuit contains only a capacitance

### Answer

### Answer

**Unity when the circuit contains only a capacitance**

**Question#30: In capacitive circuit, the current __________.**

- Lags behind voltage by π/2
- Is in phase with the voltage
- Opposite in phase of voltage by π
- Leads forward the voltage by π/2

### Answer

### Answer

**Opposite in phase of voltage by**

**π**

**Question#31: A 100 ****µF capacitor with 12V source in series having frequency 50 Hz, will offer a capacitive resistance of about_____.**

- 32ohm
- 60 ohm
- 50 ohm
- 100 ohm

### Answer

### Answer

**100 ohm**

**Question#32: If a glass plate is inserted in between the plate of a capacitor in series with a lighted bulb, the brightness of the bulb______.**

- Remains the same
- Brightness increases
- Brightness decreases
- No light

### Answer

### Answer

**Brightness increases**

**Question#33: A pure variable resistor is connected in series with a pure capacitor in series with a pure capacitor of fixed capacitance. The impedance of the circuit______.**

- Remains the same
- Becomes infinite
- Becomes zero
- Increases

### Answer

### Answer

**Becomes zero**

**Question#34: A wire of resistance R is coiled inductively so that its inductance is L. The impedance of the coil at a frequency of f is _______.**

- (R+2π fL)
^{1/2} - R+1/2πf L
- (R
^{2}+f^{2}L^{2})^{1/2} - (R
^{2}+4π^{2}f^{2}L^{2})^{1/2}

### Answer

### Answer

**(R**

^{2}+f^{2}L^{2})^{1/2}**Question#35: Ammeter connected in an AC circuit measures________. **

- The exact value of the current
- rms value of current
- The net value of the current
- The peak value of the current

### Answer

### Answer

**Net value of current**

**Question#36: When a pure inductor of inductance L and a pure capacitor of capacitance C are connected in parallel to a sinusoidal potential difference V, then potential difference across both L and C will be______.**

- Same
- Different
- At L will be more than at C
- At L will be less than at C

### Answer

### Answer

**At L will be less than at C**

**Question#37: An ideal choke would be_______.**

- Pure capacitor
- Pure conductor
- Pure resistor
- Combination of inductor and capacitor

### Answer

### Answer

**Pure conductor**

**Question#38: What is the self-inductance of a coil in which an induced emf of 2V is set up when the current changes at the rate of 4 As ^{-1}?**

- 0.5mH
- 0.5H
- 2.0H
- 8.0H

### Answer

### Answer

**0.5H**

**Question#39: The frequency of a circuit consisting of a capacitance C and a resistor R is_________.**

- C/R
- R/C
- 1/RC
- 1/R

### Answer

### Answer

**1/RC**

**Question#40: A 10ohm electric heater is connected to a 220V, 50Hz mains supply. What is the peak value of the potential difference across the heater element?**

- 220V
- 220/√2 V
- 110V
- 220√2 V

### Answer

### Answer

**220V**