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Practice MCQ Questions and answers on Physics-GK

Learn and practice General Knowledge questions and answers on Physics with very easy and understandable explanations. GK questions are very helpful different type of competitive exams. Page-3 section-13

Each section contains 100 MCQs on Physics .
21
A potentiometer wire is 100 cm long and a constant potential difference is maintained across it. Two cells are connected in series first to support one another and then in opposite direction. The balance points are obtained at 50 cm and 10 cm from the positive end of the wire in the two cases. The ratio of the emf's is :
Discuss
Answer & Solution
Answer: Option D
Solution:
In series : E1 + E2 = K(50)
In parallel : E1 - E2 = K(10)
E1 + E2 / E1 - E2 = 5/1
=> E1/E2 = 3/2
The emf's are in the ratio of 3:2.
22
Suppose voltage V is applied across a resistance R. The power dissipated in the resistance is P. Now the same voltage V is applied across a parallel combination of three equal resistors each of resistance R. Then the power dissipated in the second case will be
Discuss
Answer & Solution
Answer: Option B
Solution:
P = I2R where, I = Current, P = Electric Power, R = Resistance. Here all the resistance is put in parallel combination and in parallel combination the value of Resistance decreases and dissipation of power increase, hence 3 times more power will be dissipated(3P).
23
A galvanometer can be converted into a voltmeter by connecting with it a
Discuss
Answer & Solution
Answer: Option C
Solution:
A galvanometer is converted into a voltmeter by connecting with high resistance.
24
In superconductors, the energy gap is due to
Discuss
Answer & Solution
Answer: Option B
Solution:
In superconductors, the energy gap is due to electron-phonon interaction.
25
Electrical Pressure is also called
Discuss
Answer & Solution
Answer: Option B
Solution:
A unit of electrical pressure (or electromotive force) which causes current to flow in a circuit is called voltage. One volt is the amount of pressure required to cause one ampere of current to flow against one ohm of resistance.
26
The ''Choke' used with a tube light is basically
Discuss
Answer & Solution
Answer: Option A
Solution:
Choke is the Inductor coil/ballast which is used to induce high voltage across it. Then gas inside the starter gets ionized due to this full voltage and heats the bimetallic strip that is caused to be bent to connect to the fixed contact.
27
For photoelectric effect to take place, the metal used as the cathode should have ________
Discuss
Answer & Solution
Answer: Option C
Solution:
The photoelectric effect is the propensity of high energy electromagnetic radiation to eject electrons from a given material. The photoelectric effect has been utilized in devices called photocells, consisting of two electrodes in a sealed vacuum tube. By coating one electrode (the photocathode) with a alkali metal of low work function, a photo current could be generated even from visible light. Work function is the minimum energy needed to remove an electron from the surface of a material.
28
Which phenomena shows the particle nature of light?
Discuss
Answer & Solution
Answer: Option C
Solution:
Most commonly observed phenomena with light can be explained by waves. But the photoelectric effect suggested a particle nature for light.
29
According to the quantum theory of light, the energy of light is carried in discrete units are called
Discuss
Answer & Solution
Answer: Option D
Solution:
According to the quantum theory of light, energy of light is carried in discrete units called photons.
30
Photon is the fundamental unit/quantum of
Discuss
Answer & Solution
Answer: Option D
Solution:
A photon is an elementary particle, the quantum of light and all other forms of electromagnetic radiation. The modern photon concept was developed gradually by Albert Einstein.