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Electronics and Communication Engineering - Electronic Devices and Circuits

Exercise : Electronic Devices and Circuits - Section 8
41.

Assertion (A): The s domain impedance of a series R-L circuit is R + sL irrespective of initial conditions.

Reason (R): Complex frequency s = σ + jω.

Both A and R are true and R is correct explanation of A
Both A and R are true and R is not the correct explanation of A
A is true but R is false
A is false but R is true
Answer: Option
Explanation:

The s domain equivalent depends on initial conditions.

42.
If Va = 10 ∠0, Vb = 10 ∠ -120° and Vc = 10 ∠ -240°, then Va2 and Va0 are
10 and 0 respectively
0 and 10 respectively
0 and 0
10 and 10
Answer: Option
Explanation:

Since it is a balanced system of voltages, Va2 and Va0 must be zero.

43.
A wire has a diameter d and resistance R. If the diameter is made 3d, the length and material remaining the same, the new value of resistance will be
R/3
3 R
R/9
9 R
Answer: Option
Explanation:

Since diameter is 3d, area of cross-section is increased 9 times. Therefore, resistance is R/9.

44.
The realization of a reactance function gives
a network having inductances only
a network having capacitances only
a network having resistances only
a network having inductances and capacitances only
Answer: Option
Explanation:

Both XL and XC are reactances.

45.
The correct relation between energy and charge is
Energy = voltage/charge
Charge = Energy x voltage
Energy = voltage (charge)0.5
Energy = voltage x charge
Answer: Option
Explanation:

Energy = V x I x t since I x t = Q, energy = voltage x charge.

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