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Electronics and Communication Engineering - Electronic Devices and Circuits

Exercise : Electronic Devices and Circuits - Section 3
11.
A thermistor is used for
over voltage protection
temperature alarm circuit
automatic light control
none of the above
Answer: Option
Explanation:

The resistance of a thermistor decreases with increases in temperature. It is used to monitor hot spot temperature of electric machines.

12.
In a series RLC circuit excited by e = Em sin ωt is seen that LC < 1/ω2. Then
I lags E
I leads E
I leads E are in phase
voltage across L and C are equal
Answer: Option
Explanation:

At frequencies less than resonant frequency current leads voltage.

13.
A resistance R is connected to a voltage source Vs having internal resistance Rs. A voltmeter of resistance Rm is used to measure the voltage across R. The voltmeter will read
Answer: Option
Explanation:

Effective resistance of R and Rm is

The reading is .

14.
When a lead acid battery is being charged, the specific gravity of the electrolyte
decreases
increases
either increases or decreases
remains the same
Answer: Option
Explanation:

Specific gravity of electrolyte is highest when battery is fully charged and is lowest when discharged.

15.

Assertion (A): The response of a network to unit impulse can be obtained directly from the network function.

Reason (R): The response of a network for any input can be obtained from impulse response.

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:

Convolution integral can be used to find the response for any arbitrary input in terms of impulse response.

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