A magnet is made to oscillate with a particular frequency, passing through a coil as shown in figure. The time variation of the magnitude of e.m.f. generated across the coil during one cycle is
(a)
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(b)
|
(c)
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(d)
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Monochromatic light of frequency 5 
Hz travelling in vacuum enters a medium of refractive index 1.5. Its wavelength in the medium is
|
(a) 4000 Å |
(b) 5000 Å |
(c) 6000 Å |
(d) 5500 Å |
A potentiometer wire of length 1 m and resistance 10 W is connected in series with a cell of emf 2V with internal resistance 1 W and a resistance box including a resistance R. If potential difference between the ends of the wire is 1 mV, the value of R is
|
(a) 20000 W |
(b) 19989 W |
(c) 10000 W |
(d) 9989 W |
Which of the following shown particle nature of light
|
(a) Refraction |
(b) Interference |
(c) Polarization |
(d) Photoelectric effect |
We can reduce eddy currents in the core of transformer
|
(a) By increasing the number of turns in secondary coil |
|
(b) By taking laminated core |
|
(c) By making step-down transformer |
|
(d) By using a weak ac at high potential |
A 10 ohm electric heater operates on a 110 V line. Calculate the rate at which it develops heat in watts
|
(a) 1310 W |
(b) 670 W |
(c) 810 W |
(d) 1210 W |
A man suffering from myopia can read a book placed at 10 cm distance. For reading the book at a distance of 60 cm with relaxed vision, focal length of the lens required will be
|
(a) 45 cm |
(b) – 20 cm |
(c) – 12 cm |
(d) 30 cm |
Before the saturation state of a diode at the plate voltages of 400 V and 200 V respectively the currents are i1 and i2 respectively. The ratio i1/i2 will be
(a) 
|
(b) 2
|
(c) 2 | (d) 1/2 |
A semiconductor device is connected in a series circuit with a battery and a resistance. A current is found to pass through the circuit. If the polarity of the battery is reversed, the current drops almost to zero. The device may be
| (a) A P-type semiconductor | (b) An N-type semiconductor |
| (c) A PN-junction | (d) An intrinsic semiconductor |