Define threshold frequency.

The threshold frequency is defined as the minimum frequency of incident radiation below which the photoelectric emission is not possible completely. irrespective of the intensity of incident radiation.

Three-point charges q , – 4 q and 2 q are placed at the vertices of an equilateral triangle ABC of side l as shown in the figure. Find out the amount of the work done to separate the charges at infinite distance.

The work done to separate the charges to infinity = Change in the potential energy of the system ⇒ W = ∆ P . E . = U f - U i The initial potential energy of the system, U i = 1 4 πε 0 ( - 4 q ) ( 2 q ) l + ( 2 q ) ( q ) l + ( - 4 q ) ( q ) l U i = q 2 4 πε 0 - 8 + 2 - 4 l = - 10 q 2 4 πε 0 l Final potential energy, U f = 0 Work done, W = U f - U i = 0 - - 10 q 2 4 πε 0 l = 10 q 2 4 πε 0 l Thus, W = 5 q 2 2 πε 0 l

Define mutual inductance and write its S . I . unit.

According to the Faraday's Law of electromagnetic induction, the induced emf is given by e = - M dI dt , where M = Coefficient of mutual induction, and I is the current. The mutual inductance is equal to the induced emf set up in one coil when the rate of change of current flowing through the other coil is unity. SI unit: H e n r y o r W e b e r a m p e r e - 1 o r v o l t s e c a m p e r e - 1

A small town with a demand of 1200 K W of electric power of 220 V is situated 20 K m away from an electric plant generating power at 440 V . The resistance of the two wireline carrying power is 0 . 5 Ω p e r k m . The town gets power from the line through a 4000 - 220 V step-down transformer at a sub-station in the town. Estimate the line power loss in the form of heat.

RMS means Root Mean Squared voltage. This means taking the root of the mean of the square of the instantaneous voltage. RMS voltage is also known as Effective voltage which is defined as the overall effective value of the alternating current or alternating voltage RMS current in the coil I = P V Given, power P = 1200 kW = 1200 × 10 3 W and V = 4000 V , Resistance per unit length of the wire is 0 . 5 Ω p e r k m Length of wire line = 20 × 2 = 40 k m Resistance of wire line, R = 40 x 0 . 5 = 20 Ω I = 1200 × 10 3 4000 = 300 A The line power loss in the form of heat. P = I 2 R = 300 2 × 20 = 1800 kW

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Physics Crash Course (Based on Revised Syllabus-2023)>Chapter 16 - Sample Paper 2>Exercise>Q 14

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An alternating voltage given by $V = 140 \sin (314 t)$ is connected across a pure resistor of $50 Ω$ . The RMS current through the resistor is

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Important Questions on Sample Paper 2

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Physics Crash Course (Based on Revised Syllabus-2023)>Chapter 16 - Sample Paper 2>Exercise>Q 15

The capacity of the capacitor

1 μF

has charge

40 μC

. The energy stored in the capacitor is :

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Physics Crash Course (Based on Revised Syllabus-2023)>Chapter 16 - Sample Paper 2>Exercise>Q 19

Name the e.m waves which are suitable for radar systems used in aircraft navigation. Write the range of frequency of these waves.

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Physics Crash Course (Based on Revised Syllabus-2023)>Chapter 16 - Sample Paper 2>Exercise>Q 20

Why do the iron fillings align themselves in a certain pattern around a magnet ?

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Physics Crash Course (Based on Revised Syllabus-2023)>Chapter 16 - Sample Paper 2>Exercise>Q 21

Calculate the minimum amount of energy which a gamma ray photon should have for the production of an electron and positron pair.

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Physics Crash Course (Based on Revised Syllabus-2023)>Chapter 16 - Sample Paper 2>Exercise>Q 22

What is quantum mechanics?

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Physics Crash Course (Based on Revised Syllabus-2023)>Chapter 16 - Sample Paper 2>Exercise>Q 23

Find the angle of reflection through second mirror?

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Physics Crash Course (Based on Revised Syllabus-2023)>Chapter 16 - Sample Paper 2>Exercise>Q 24

Explain with a proper diagram how an ac signal can be converted into dc(pulsating) signal with an output frequency double the input frequency using the PN junction diode. Give its input and output waveforms.

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Physics Crash Course (Based on Revised Syllabus-2023)>Chapter 16 - Sample Paper 2>Exercise>Q 25

What is the purpose of heavy doping of $p -$ and $n -$ sides of a zener diode?