Alternating Current — Physics STD 12 Science — Question

Two point positive charge of 1C are located at a distance 1 m from each other in the air. The value of the electric force of repulsion acting between the charges will be-

A current I is passing through a wire having two sections P and Q of uniform diameters d and d/2 respectively.  If the mean drift velocity of electrons in sections P and Q is denoted by v_P and v_Q respectively, then

(a) vP = vQ

(b) vP =  vQ

(c) vP =  vQ

(d) vP = 2 vQ

A light wave is incident normally over a slit of width 24 . The angular position of second dark fringe from the central maxima is 30^o. What is the wavelength of light

(a) 6000 Å

(b) 5000 Å

(c) 3000 Å

(d) 1500 Å

Which experiment seemed to make it clear that light propogates as a wave?

An electromagnetic wave travels along z-axis. Which of the following pairs of space and time varying fields would generate such a wave

(a)

(b)

(c)

(d)

The inward and outward electric flux for a closed surface in units of   are respectively   and    Then the total charge inside the surface is [where  = permittivity constant]

(a)

(b) -

(c)

(d)

In a nuclear reactor, the fuel is consumed at the rate of 1 mg/s. The power generated in kilowatt is

(a) 9

(b) 9

(c) 9

(d) 9

The intrinsic semiconductor becomes an insulator at

(a) 0℃

(b) --100℃

(c) 300 K

(d) 0 K

A radioactive element emits 200 particles per second. After three hours 25 particles per second are emitted. The half life period of element will be

(a) 50 minutes

(b) 60 minutes

(c) 70 minutes

(d) 80 minutes

In a diode valve, the state of saturation can be obtained easily by

(a) High plate voltage and high filament current

(b) Low filament current and high plate voltage

(c) Low plate voltage and high cathode temperature

(d) High filament current and high plate voltage