Resonance Questions

There is a particular kind of frequency in which the charged particles, objects and mechanical systems have a tendency to vibrate and this frequency is named as the natural frequency or the resonant frequency of that object. Now comes the phenomenon of resonance which can be explained as: When an object that is previously vibrating at some specific frequency, and when light or a sound wave hits that object, and also if the frequency of the incident light matches the resonant frequency of that object it is hitting, then this phenomenon of matching of frequencies will be named resonance.

Resonance in physics is defined as: At a definite frequency of operation, when an exterior force or a vibrating system forces another system around it to vibrate with superior amplitude, then this phenomenon is called resonance. The resonant frequency is basically a natural frequency where a particular medium vibrates at the maximum amplitude. Usually, it is denoted as f₀. Resonance is observed in objects that are in equilibrium with forces acting on them and also under perfect conditions, they should have the ability to keep the vibrations for a long time.

To find the resonant frequency of a single continuous-wave, the following formula is used:

Where,

v is the wave velocity

λ is the distance of the wavelength.

Important Questions on Resonance

1) The frequency with which forced periodic oscillations to oscillate is known as ______.

a) Frequency of forced oscillator

b) Natural frequency

c) No definite frequency

d) Sum of natural frequency and frequency of the forced oscillator.

Correct Option: (a)

Explanation: The oscillations made by the body in the case of forced oscillations do not depend on their natural frequency; instead, they oscillate with the frequency of the forced oscillator.

2) When the frequency of forced oscillations is close to the natural frequency, then resonance occurs.

a) True

b) False

Correct Option: (a)

Explanation: The phenomenon of oscillation with improved amplitude when the frequency of the forced oscillator is near to natural frequency is known as resonance. Hence, the vibrations of the external oscillator that match the vibrations of particles that oscillate are the reason for this increase. Thus, there is a net increase in vibrations.

3) More the constant damping value, the more will be the amplitude at resonance. Is it true or false?

a) True

b) False

Correct Option: (b)

Explanation: For higher damping values, the effect of forced oscillations will be lesser in increasing the amplitude close to the natural frequency. Therefore, the amplitude at resonance will be less if the value of the damping constant is more.

4) If the current is_____ with the applied voltage, the circuit is said to be in resonance.

a) Out of phase

b) In phase

c) 90⁰ out of phase

d) 45⁰ out of phase

Correct Option: (b)

Explanation: If the current is in phase with the applied voltage, then the circuit is said to be in resonance. And if the current is out of phase with the applied voltage, then the circuit is not in resonance. Mainly in the area of communications, the study of resonance is very useful.

5) The condition for series resonance in a series resonance circuit is?

a) X_L = 2

b) X_C = 2

c) X_L = X_C

d) X_L = -X_C

Correct Option: (c)

Explanation: Series resonance in a series resonance circuit occurs when capacitive reactance is equal to the inductive reactance that is X_L = X_C.

6) In a series resonance circuit, what will be the impedance if X_L = X_C?

a) Purely inductive

b) Purely resistive

c) Purely capacitive

d) Inductive and capacitive

Correct Option: (b)

Explanation: The impedance is purely resistive when X_L = X_C in a series resonance circuit. The current lags behind or leads the applied voltage in a series RLC circuit, depending on the values of X_L and X_C.

7) The voltage across the capacitor is _______ the voltage across the inductor at the resonant frequency.

a) Lesser than

b) Greater than

c) Greater than or equal to

d) Equal to

Correct Option: (d)

Explanation: The voltage across the capacitor at the resonant frequency is equal to the voltage across the inductor. The circuit is said to be in resonance if one of the parameters of the series RLC circuit is varied in such a way that the applied voltage is in phase with the current in the circuit.

8) The voltage across capacitor and inductor are ______ with each other in a series RLC circuit.

a) In phase

b) 90⁰ out of phase

c) 180⁰ out of phase

d) 30⁰ out of phase

Correct Option: (c)

Explanation: The voltage across capacitor and inductor are 180⁰ out of phase with each other in a series RLC circuit. The frequency at which the resonance happens is termed the resonant frequency.

9) In a series RLC circuit, the voltage across the LC combination will be ________.

a) 1

b) 2

c) 0

d) 3

Correct Option: (c)

Explanation: The voltage across the LC combination in a series RLC circuit is 0V because the voltage across the capacitor and inductor are 180⁰ out of phase with each other.

10) In a series resonant circuit, the expression of resonant frequency is _______.

a) 1/(2π√LC)

b) 3π√LC

c) 1/(3π√L)

d) 1/(2π√C)

Correct Option: (a)

Explanation: The expression of resonant frequency is = 1/(2π√LC). In a series RLC circuit, keeping L and C constant resonance may be produced by varying the frequency.

Practice Questions

1) What is resonance frequency?

2) What is the cause of the occurrence of resonance?

3) Explain how a bridge collapses due to resonance.

4) Give some examples of resonance.

5) What is electrical resonance?

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