Tag: physics

Questions Related to physics

According to special theory of relativity which one is not an absolute quantity?

relativistic mechanics option a: relativity physics

  1. time

  2. mass

  3. height

  4. both a and b

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Correct Option: D
Explanation:
According to classical physics time and mass are not an absolute quantity

The supply voltage to an opamp is +-15volts. The opamp is connected as an inverting amplifier of gain -20. The output voltage for an input voltage of 20mV is:

properties of an ideal op-amp electronics physics the operational amplifier (op-amp)

  1. -400 mV

    • 400 mV

  3. -200 mV

  4. +200 mV

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Correct Option: A
Explanation:

Voltage gain and output voltage are related by the formula $A _v=\dfrac{output \ voltage}{input \ voltage}$. Substituting the value of input voltage, we get, output voltage = - 20 x 20mV = -400 mV

The advantage of having an infinite bandwidth in an Ideal op amp is

properties of an ideal op-amp electronics physics the operational amplifier (op-amp)

  1. Signals can be amplified without attenuation

  2. Output common-mode noise voltage is zero

  3. Output voltage occurs simultaneously with input voltage changes

  4. Output can drive infinite number of device

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Correct Option: A
Explanation:

 An ideal op-amp has infinite bandwidth. Therefore, any frequency signal from 0 to $\infty$ Hz can be amplified without attenuation.

An ideal Opamp is an ideal

properties of an ideal op-amp electronics physics the operational amplifier (op-amp)

  1. Current controlled current source

  2. current controlled voltage source

  3. Voltage controlled voltage source

  4. Voltage controlled current source

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Correct Option: C
Explanation:

The ideal opamp voltage is maintained constant. It is controlled by the input voltage. Thus the output of an opamp is controlled by the source (input) voltage

The slew rate of an ideal opamp is

properties of an ideal op-amp electronics physics the operational amplifier (op-amp)

  1. Infinite

  2. Zero

  3. Half of the voltage gain

  4. 10 times the voltage gain

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Correct Option: B
Explanation:

In an ideal opamp, output follows the input instantly and hence the time delay is zero. slew rate is calculated as the ratio of change in voltage at the output to time taken for this action to take place. If time delay is zero, the slew rate will be infinite

An opamp has a supply voltage of 9V AND -9V at its power terminals. What is the maximum output voltage one can obtain by varying the voltage across the inverting and non inverting terminals 

properties of an ideal op-amp electronics physics the operational amplifier (op-amp)

  1. Greater than 9V

  2. 9V

  3. 18V

  4. Can be infinity depending on the voltage gain of the opamp

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Correct Option: B
Explanation:

maximum voltage that can obtained will be equal to the supply voltage w.r.t ground and beyond which the amplifier will saturate

An AC signal with frequencies 1000 Hz, 1500 Hz and 2500 Hz are fed to the inverting terminal of an opamp. The voltage level of all these signals are 2V. If 1000 Hz signal is amplified by 20 times, then

properties of an ideal op-amp electronics physics the operational amplifier (op-amp)

  1. 2500 Hz signal will get amplified by 50 times

  2. 2500 Hz signal will get amplified by 20 times

  3. 1500 Hz signal will get amplified by 15 times

  4. 2500 Hz signal will get amplified by 10 times

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Correct Option: B

The ideal opamp has the following characteristics

properties of an ideal op-amp electronics physics the operational amplifier (op-amp)

  1. Input resistance = Infinity; Voltage gain = Infinity

  2. Input resistance = zero; Voltage gain = Infinity

  3. Input resistance = zero; Voltage gain = zero

  4. Input resistance = Infinity; Voltage gain = zero

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Correct Option: A
Explanation:

The ideal op-amp has infinite high input resistance and infinite voltage gain.

The ideal op-amp will have infinite voltage gain.Op-amp are devices that many times are used to function as amplifiers. A voltage is input into the op-amp and as output, it produces the voltage amplified.
An ideal op-amp will have infinite high input resistance.This will ensure that the op-amp causes no loading in the circuit.

The open loop voltage gain in an opamp 

properties of an ideal op-amp electronics physics the operational amplifier (op-amp)

  1. reduces if voltage across the inverting and non inverting terminal are same

  2. reduces if voltage across the inverting terminal is zero

  3. increases if voltage across the inverting and non inverting terminal are same

  4. remains the same, if voltage across any of these terminals are changed

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Correct Option: C
Explanation:

Open loop voltage gain is given by $A _v=\dfrac{V _0}{V _+-V _-}$. If $V _+=V _-$, Voltage gain becomes infinity or very high. thus voltage gain increases

Which of the following electrical characteristics is not exhibited by an ideal op-amp?

properties of an ideal op-amp electronics physics the operational amplifier (op-amp)

  1. Infinite voltage gain

  2. Infinite bandwidth

  3. Infinite output resistance

  4. Infinite slew rate

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Correct Option: C
Explanation:

An ideal op-amp exhibits zero output resistance so that output can drive an infinite number of other devices.