21.

In producing chlorine by electrolysis 100 kW power at 125 V is being consumed. How much chlorine per minute is liberated (ECE of chlorine is 0.367 x 10^-6 KgC^-1)

• 1.76 x 10^-3 kg

• 9.67 x 10^-3 kg

• 17.61 x 10^-3 kg

• 17.61 x 10^-3 kg

An alpha nucleus of energy mv²/2 bombards a heavy nuclear target of charge Ze. Then the distance of closest approach for the alpha nucleus will be proportional to 

• 1/Ze

• v²

• 1/m

• 1/v⁴

If ΔU and ΔW represent the increase in internal energy and work done by the system respectively in the thermodynamical process, which of the following is true?

• ΔU = - ΔW, in a adiabatic process

• ΔU = ΔW, in an isothermal process

• ΔU = ΔW, in an adiabatic process

• ΔU = ΔW, in an adiabatic process

The total radiant energy per unit area, normal to the direction of incidence, received at a distance R from the centre of a star of radius r, whose outer surface radiates as a black body at a temperature T K is given by

• σr²T⁴/R²

• σr²T⁴/4πR²

• σr⁴T⁴/r⁴

A beam of cathode rays is subjected to crossed Electric (E)  and magnetic field (B). The fields are adjusted such that the beam is not deflected. The specific charge of the cathode rays is given by  

(Where V is the potential difference between cathode and anode)

• B²/2VE²

• 2VB²/E²

• 2VE²/B²

• 2VE²/B²

A thin ring of radius R metre has charge q column uniformly spread on it. The ring rotates about its axis with a constant frequency of  f revolution/s. The value of magnetic induction in Wb m^-2 at the centre of the ring is

• μ_oq f/ 2π R

• μ_oq / f 2π R

• μ_oq / 2 f R

• μ_oq / 2 f R

A conducting circular loop is placed in a uniform magnetic field, B = 0.0025 T with its plane perpendicular to the loop. The radius of the loop is made to shrink at a constant rate of 1 mms^-1. The induced emf when the radius is 2 cm, is

• 2 πμ V

• πμ V

• πμ V/2

• πμ V/2

A potentiometer circuit is set up as shown. The potential gradient across the potentiometer wire is k volt /cm and the ammeter, present in the circuit, reads 1.0 A when the two-way key is switched off. The balance points, when the key between the terminals (i) 1 and 2 (ii) 1 and 3, is plugged in, are found to be at lengths  l₁ and l₂ cm respectively. The magnitudes, of the resistor R and X, in ohm, are then, equal respectively, to

 

• k (l₂ -l₁) and kl₂

• kl₁ and k (l₂-l₁)

• k (l₂ - l₁) and kl₁

• k (l₂ - l₁) and kl₁

A galvanometer has a coil of resistance 100 Ω and gives a full-scale deflection for 30 mA current. If it is to work as a voltmeter of 30 V range, the resistance required to be added will be

• 900 Ω

• 1800

• 500 Ω

• 500 Ω

Which of the following statement is false or the properties of electromagnetic waves?

• Both electric and magnetic field vectors attain the maxima and minima at the same place and same time

• The energy in electromagnetic waves is divided equally between electric and magnetic  vectors

• Both electric and magnetic field vectors are parallel to each other and perpendicular to the direction of propagation of wave

• Both electric and magnetic field vectors are parallel to each other and perpendicular to the direction of propagation of wave