Following is the collection of all TN State Board Exam Questions (for Plus Two Physics) that appeared from March 2006 to September 2014. Answers for the MCQs and Problems will be uploaded soon. Pl note that the circuit diagrams are missing in this file; the same can be viewed in the pdf file uploaded in the same name as this file.
UNIT – IV E.M. INDUCTION & A.C. MAR – 2006 TO SEP – 2014
PART – I
Electromagnetic induction is not used M06, J07, M08, J08, S08, J09, S11, J12, M14 a] transformer b] room heater c] A C generator d] choke coil.
The angle between the area vector A and the plane of the area A is M06, J09, S13
a] π b] 2π c] π / 2 d] zero
If the flux associated with a coil varies at the rate of 1 Wb / min. then the induced emf is M06
a] 1 V b] 1 / 60 V c] 60 V d] 0.60 V
The average power consumed over one cycle in an a.c. circuit is M06, S14
a] E rms I rms b] E rms I rms cos φ c] E rms I rms sin φ d] E o I o cos φ
In LCR series a.c. circuit, the phase difference between current and voltage is 300 . The reactance of the circuit is 17.32 Ω. The value of the resistance is J06, S13
a] 30 Ω b] 10 Ω c] 17.32 Ω d] 1.732 Ω
An emf of 12 V is induced when the current in a coil changes from 2 A to 6 A in 0.5 s. The coefficient of self-induction of the coil is J 06
a] 1.5 H b] 6 H c] 0.3 H d] 30 H
In an a.c. circuit with an inductor J 06
a] voltage lags current by π / 2 b] voltage leads current by π
c] voltage and current are in phase d] current lags voltage by π / 2
The unit henry can also be written as J06, J11, S11, J14
a] V s A –1 b] Wb A –1 c] Ω s d] all of these.
The generator rule is S06, J 07
a] Fleming’s left hand rule b] Fleming’s right hand rule
c] Maxwell’s cork screw rule d] Right hand palm rule
The power loss is less in transmission line when S06, M13
a] voltage is less but current is more b] both voltage and current are more
c] voltage is more but current is less d] both voltage and current are less
In an a.c. circuit, the current I = I0 sin ( ωt - π/2 ) lags behind the e.m.f. e = E0 sin ( ωt + π/2 ) by S 06
a] 0 b] π / 4 c] π / 2 d] π
In a step-up transformer the input voltage is 220 V and the output voltage is 11 kV. The ratio of number of turns in primary to secondary is S 06, J 07
a] 50 : 1 b] 1 : 50 c] 25 : 1 ( or 20 : 1) d] 1 : 25 ( or 22:1)
In an LCR circuit when X L = X C, the current M 07
a] is zero b] is in phase with the voltage
c] leads the voltage d] lags behind the voltage.
Transformer works on M 07, S 07, J 10, M 11, M14, S14
a] both AC and DC b] AC more effectively than DC c] AC only d] DC only
Lenz law is in accordance with the law of conservation of M07, M08, M11, J12, S13
a] energy b] charge c] momentum d] angular momentum
The self-inductance of a straight conductor is M07, M09, J10, S11, J12, M13, J13
a] zero b] infinity c] very large d] very small
In an AC circuit with capacitor only, if the frequency of the signal is zero, then the capacitive reactance is J 07
a] infinity b] zero c] finite maximum d] finite minimum
The core used in audio frequency choke is S 07, S 09
a] iron b] carbon c] lead d] steel (or air )
The reactance offered by a 300 mH inductor to an AC supply of frequency 50 Hz is S 07
a] 1046 Ω b] 94.2 Ω c] 9420 Ω d] 104.6 Ω
The r.m.s. value of an a.c. voltage with a peak value of 311 V is S 07
a] 110 V b] 220 V c] 50 V d] 70.7 V
In a transformer, eddy current loss is minimized by using M 08
a] laminated core made of mumetal b] laminated core made of stelloy
c] shell type core d] thick copper wires.
A power of 11,000 W is transmitted at 220 V. The current through the line wires is M 08
a] 50 A b] 5 A c] 500 A d] 0.5 A
Which of the following cannot be stepped up in a transformer? J 08, S 09, J14
a] Input current b] Input voltage c] Input power d] All of these
For a d.c. circuit, the value of the capacitive reactance X c is J 08
a] zero b] infinity c] π / 2 d] π
The Q – factor of an a.c. circuit containing a resistance R, inductance L and capacitance C is J 08
a] 1/√LC b] 1/R √(C/L) c] 1/R √(L/C) d] 1/√LR
In a 3-phase AC gen. the three coils are fastened rigidly together and are displaced from each other by an angle of S 08
a] 900 b] 1800 c] 1200 d] 3600.
A D.C. of 5A produces the same heating effect as an A.C. of ________ current. S08, J13
a] 50 A rms b] 5 A peak c] 5A rms d] 5 √2 A rms
In RLC series circuit, at resonance S 08
a] current is minimum b] impedance is maximum
c] circuit is purely inductive d] current is in phase with voltage
A D.C. of 5A produces the same heating effect as an A.C. of ________ current. M 09
a] 50 A rms b] 5 A peak c] 15A rms d] none of these
The Q-factor of a series resonant circuit M 09
a] Q = 1/L √(R/C) b] Q = 1/R √(L/C) c] Q = 1/L √(R/C) d] Q = 1/C √(L/R)
In an ac circuit M09, S11, M14
a] the average value of current is zero b] the average value of square of current is zero
c] the average power dissipation is zero d] the rms current is two times of peak current
Which of the following devices does not allow D.C. to pass through? J09, M10, S10, J11, J12, M13, J13
a] Capacitor b] Inductor c] Resistor d] All of these
A coil of area of cross-section 0.5 m 2 with 10 turns is in a plane which is perpendicular to a uniform magnetic field of 0.2 Wb/m2 . The magnetic flux through the coil is J 09
a] 100 Wb b] 10 Wb c] 1 Wb d] zero
In LCR series circuit, at resonance S 09
a] impedance (z) is maximum b] current is minimum
c] impedance (z) is equal to R d] ν_0 = 1/√(ε_0 )
An e.m.f. of 12 V is induced when the current in a coil changes at the rate of 40 A s –1 . The coefficient of self-induction of the coil is S 09, S10
a] 0.3 H b] 0.003 H c] 30 H d] 4.8 H
A coil of area of cross-section 0.5 m2 with 10 turns is in a plane which is parallel to a uniform magnetic field of 0.2 Wb/m2. The flux through the plane is M 10
a] 100 Wb b] 10 Wb c] 1 Wb d] zero
The part of the A.C. generator that passes the current from the coil to the external circuit is
M 10, S13, J14
a] field magnet b] split rings c] slip rings d] brushes
The r.m.s. value of the A.C. flowing through a resistor is 5 A. Its peak value is M 10
a] 3.536 A b] 70.7 A c] 7.07 A d] 7 A
In an A.C. circuit, average power consumed is 200 W and the apparent power is 300 W. Power factor is J 10
a] 1.5 b] 0.66 c] 0.33 d] 1.
The effective value of alternating current is J 10
a] I_( 0)/2 b] I_( 0)/√2 c] I0 √2 d] 2 I0
In a series LCR circuit, at resonance S 10
a] X L = X C b] X L > X C c] X L < X C d] ω = 1 / L C
A rectangular coil is uniformly rotated in a uniform magnetic field such that the axis of rotation is perpendicular to the direction of the field. When the plane of the coil is perpendicular to the field, then S 10
a] magnetic flux is zero, induced emf is zero
b] magnetic flux is maximum, induced emf is maximum
c] magnetic flux is maximum, induced emf is zero
d] magnetic flux is zero, induced emf is maximum.
In an a.c. circuit, the voltage leads the current by a phase of π/2 , then the circuit has M11
a] only an inductor (L) b] only a capacitor (C)
c] only a resistor (R) d] L, C and R in series.
The resonant frequency of RLC circuit is γ_0 . The inductance is doubled. The capacitance is also doubled. Now the resonant frequency of the circuit is J11
a] 2 γ_0 b] γ_0/2 c] γ_0/4 d] γ_0/√2 .
When the frequency of an a.c. circuit increases, the capacitive reactance offered by a capacitor connected in the circuit J11
a] increases b] decreases c] remains the same d] becomes zero.
The instantaneous emf and current equations of an a.c. circuit are respectively e = 200 sin (ωt+ π/3) and i = 10 sin ωt. The average power consumed over one complete cycle is: M13
a] 2000 W b] 1000 W c] 500 W d] 707 W.
In a series RLC circuit, the instantaneous values of current and emf are I = I0 sin (ωt − π/3) and
e = E0 sin ωt respectively. The phase difference between current and voltage is: J13
a] zero b] 1800 c] 600 d] 450.
If an emf of 25 V is induced when the current in the coil changes at the rate of 100 As^(―1), then the coefficient of self induction of the coil is M14
a] 0.3 H b] 0.25 H c] 2.5 H d] 0.25 mH.
Eddy current loss in a transformer can be minimised by using a laminated core made of : J14
a] stelloy b] mumetal d] soft iron d] silicon steel.
In an AC circuit, the applied emf e = E0 sin ( ωt + π/2 ) leads the current I = I0 sin ( ωt - π/2 ) by S14
a] π/2 b] π/4 c] π d] 0
In LCR series a.c. circuit, the phase difference between current and voltage is 600 . The net reactance of the circuit is 17.32 Ω. The value of the resistance is S14
a] 30 Ω b] 17.32 Ω c] 10 Ω d] 1.732 Ω
PART – II THREE – MARK QUESTIONS
Calculate the mutual inductance between two coils when a current of 4 A changing to 8 A in 0.5 s in one coil, induces an e.m.f. of 50 mV in the other coil. M06, M09
Mention the methods of producing induced e.m.f. M 06, S10, M11, M12
State Faraday’s laws of electromagnetic induction. J06, S13, S14
An aircraft having a wingspan of 20.48 m flies due north at a speed of 40 m s −1. If the vertical component of earth’s magnetic field at the place is 2 × 10 − 5 T, Calculate the emf induced between the ends of the wings. J06, M 08, J10, S10, M11
Define quality factor. S06, J11, J12, J13
The wings of an aeroplane are 10 m apart. The plane is moving horizontally towards north at a place where the vertical component of earth’s magnetic field is 3 x 10 – 5 T. Calculate the induced emf set up between tips of its wings if the velocity of the aeroplane is 720 km/hr. [ S 06 ]
State Fleming’s right hand rule. M07, J11
A coil of area of cross section 0.5 m 2 with 10 turns is in a plane which is perpendicular to a uniform magnetic field of 0.2 Wb/m 2. Calculate the flux through the coil. M07
Define r.m.s. value of alternating current. J07, S09, M13, J14
State Faraday’s laws of electromagnetic induction. J07, S07
Why can a d.c. ammeter not read a.c.? S07
What is electromagnetic induction? M08
Give the differences between AF choke and RF choke. J08
A capacitor of capacitance 2 μF is in an a.c. circuit of frequency 1000 Hz. If the r.m.s. value of the applied emf is 10 V, find the effective current flowing in the circuit. J08, S13
State Lenz law in electromagnetic induction. S08, J10, M14
An ideal transformer has a transformer-ratio of 1 : 20. If the input power and the primary voltage are 600 mW and 6 V respectively, find the primary and secondary currents. S08
State Fleming’s right hand rule. M09, S09, M10
Define coefficient of self-induction. J09
Calculate the capacitive reactance of a capacitor of capacitance 2 µF in an A.C. circuit of frequency 1000 Hz. J09
An emf of 5 V is induced when the current in the coil changes at the rate of 100 As^(―1). Find the coefficient of self-induction of the coil. M10
A capacitor blocks d.c. but allows a.c. Why? S11
Write the equation of a 25 cycle current sine wave having an rms value of 30 A. S11, M12, J13
Define the unit of self-inductance. J12
A solenoid of length 1 m and 0.05 m diameter has 500 turns. If a current of 2 A passes through the coil, calculate the coefficient of self-induction of the coil. M13
Magnetic field through a coil having 200 turns and cross-sectional area 0.04 m^2 changes from
0.1 Wb•m^(―2) to 0.04 Wb•m^(―2) in 0.02 s. Find the induced emf. M14
11 kW power is transmitted at 22000 V through a wire of resistance 2 Ω. Calculate the power loss. J14
A train runs at a speed of 180 km/hr on a railway track with the two rails insulated from each other and the ground and connected to millivoltmeter. If the vertical component of the Earth’s magnetic field
is 0.2x10—4 Wb/m2 and the distance of separation between the rails is 1 m, what would be the reading in the voltmeter ? S14
PART – III FIVE-MARK QUESTIONS
Obtain the phase relation between current and voltage in an a.c. circuit with an inductor only. [ graph not necessary] M06, M08
What are the reasons for various energy losses in a transformer? Explain how they can be minimised? J06, S06, S09, S10, M11, M13, S14
Give any two applications of eddy currents. M07, M10
Explain how an e.m.f. can be induced by changing the area enclosed by a coil. J07, S07, S08, M09, J13
Explain the mutual induction between two long solenoids. (Obtain the expression for the mutual inductance of two long solenoids). J08 , (M12)
An a.c. generator consists of a coil of 10,000 turns and of area 100 cm 2. The coil rotates at an angular speed of 140 rpm in a uniform magnetic field of 3.6 × 10 − 2 T. Find the maximum value of the emf induced. J09
Define efficiency of a transformer. Explain the various energy losses in a transformer. How are they minimized? J10
State Faraday’s laws and Lenz law in electromagnetism. J11
Obtain an expression for the current flowing in a circuit containing resistance only to which an alternating emf is applied. Find the phase relationship between voltage and current. S11, J12
Obtain an expression for the energy associated with an inductor. S13
Obtain an expression for the self-inductance of a long solenoid. M14
Mention the applications of eddy currents and explain any two of them. J14
PART – IV TEN-MARK QUESTIONS
Explain the principle, construction and theory of a transformer. (Diagram not necessary). Define its efficiency. [Mention the energy losses]. [M06], S13
A source of alternating emf is connected to a series combination of resistor R, inductor L and capacitor C. Obtain with the help of a voltage phasor diagram and impedance diagram, the expressions for [i] effective voltage, ii] impedance and iii] phase relation between current and voltage. J06, J09, J14
In an a.c. circuit containing a capacitor, the instantaneous emf is e = E 0 sin ωt. Obtain the expression for instantaneous current. Explain the phase relation between emf and current by graph. S06
Describe the principle, construction and working of a single-stage a.c. generator. M07, J07, S07, M08, S10, M11, J11, J12, J13, M14
Discuss with theory, the method of inducing emf in a coil by changing its orientation with respect to the direction of the magnetic field. J08, S09, M10, J10, S11, M13, S14
Obtain the phase relation between voltage and current in an AC circuit containing a pure inductance. Draw the necessary graph. S08
What are eddy currents? Explain their applications. How are they minimized? M09
Write the principle and explain the construction and working of a transformer. Define its efficiency.
M12
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