Question 1 Why it is not possible to have electrolysis by A.C?
Solution
An alternating current reverses its direction after each half cycle. Therefore on passing A.C through a solution, the motion of the positive and negative ions become vibratory .So ions are not separated. So that is the reason electrolysis does not happen in A.C. Also Batteries cannot be charged through A.C for this reason only.
Question 2 What is the value of the inductive reactance X
L in a DC circuit?
Solution
inductive reactance XL is given by
XL=ωL
For DC ,ω=0, So XL=0
Question 3 Which of the these works on the principle of self-induction?
a) Transformer
b) Transistor
c) choke
d) None of these
Solution
Answer is (c)
Question 4 If the velocity of the object is zero,the acceleration would also be zero
a) True
b) False
Solution
False.
Question 5 What is true of any AC circuit?
a) None of these
b) The power dissipation happens in resistance only in AC circuit
c) The algebraic sum of the rms voltage across the different element of the circuit is equal to the applied rms voltage
d) The algebraic sum of the instantaneous voltage across the different element of the circuit is equal to the applied instantaneous voltage
Solution
Answer is (b)
C and d are incorrect as the voltage across different elements are not in phase.
Question 6 Transformers are used
a) To step up or step down ac voltage
b) To convert a.c to d.c
c) To step up d.c voltage
d) To convert d.c to a.c
Solution
(a)
Question 7 What is true of AC GENERATOR?
a) It works on the principle of electromagnetic induction
b) The mechanical energy of the rotation is converted into electrical energy
c) A pair of slip rings are used in the AC generator
d) All the above
Solution
Answer is (d)
Question 8 An alternating voltage V=200sin300t is applied across a series combination of R=10Ω and L=800mH.
a) The impedence of the circuit is 240.2Ω
b) Power factor is given by .05
c) The peak current in the circuit is .8326 A
d) None of these
Solution
(a) and (c)
Formula used
$Z=\sqrt {R^2 + (\omega L)^2}$
$i_0=\frac {V}{Z}$
$cos \phi =\frac {R}{Z}$
Question 9 In an series LC circuit, the voltage across the L and C are
a) 180 out of phase
b) 90 out of phase
c) are in same phase
d) 45 out of phase
Solution
(a)
Question 10 Let A and B are the heat production of the electric heater in AC and DC of same voltage.
a) A=B
b) A> B
c) A <B
d) none of the above
Solution
(c)
Question 11 An inductor having a reactance of 25 and a resistance R gives off heat at the rate of 10W when it carries a current of 0.50A (rms). What is the impedance of the inductor?
Question 12 At the moment depicted in the LC circuit the current is non-zero and the capacitor plates are charged (as shown in the figure below). The energy in the circuit is stored
a) only in the electric field and is decreasing.
b) only in the electric field and is constant.
c) only in the magnetic field and is decreasing.
d) only in the magnetic field and is constant.
e) in both the electric and magnetic field and is constant.
f) in both the electric and magnetic field and is decreasing.
Solution
(e)
Class 12 Maths
Class 12 Physics
