A body at a temperature of 728 ° C and has surface area 5 cm2, radiates 300 J of energy each minute. The emissivity is
(given Boltzmann constant 
)
1. e = 0.18
2. e = 0.02
3. e = 0.2
4. e = 0.15
A body at a temperature of 728 ° C and has surface area 5 cm2, radiates 300 J of energy each minute. The emissivity is
(given Boltzmann constant)
(given Boltzmann constant
)1. e = 0.18
2. e = 0.02
3. e = 0.2
4. e = 0.15
Subtopic: Stefan-Boltzmann Law |
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Considering normal incidence of ray, the equivalent refractive index of combination of two slabs shown in figure is
1. 1.8
2. 1.43
3. 2
4. None of the above
2. 1.43
3. 2
4. None of the above
Subtopic: Refraction at Plane Surface |
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Three particles having charges in the ratio of 2 : 3 : 5 produce the same point on the photographic film in Thomson experiment. Their masses are in the ratio of
1. 2 : 3 : 5
2. 5 : 3 : 2
3. 15 : 10 : 6
4. 3 : 5 : 2
Subtopic: Various Atomic Models |
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A black body emits heat at the rate of 20 W. When its temperature is 727 ° C. Another black body emits heat at the rate of 15W, when its temperature is 227 º C. Compare the area of the surface of the two bodies, if the surrounding is at NTP.
1. 16 : 1
2. 1 : 4
3. 12 : 1
4. 1 : 12
Subtopic: Conduction |
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The pressure on a square plate is measured by measuring the force on the plate and the length of the sides of the plate by using the formula . If the maximum errors in the measurement of force and length are 4% and 2% respectively, then the maximum error in the measurement of pressure is
1. 1%
2. 2%
3. 8%
4. 10%
Subtopic: Errors |
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The transfer ratio β of a transistor is 50. The input resistance of the transistor, when used in the common emitter mode is 1kΩ. The peak value of the collector alternating current for an input peak voltage of 0.01 V is
1. 
Subtopic: Transistor (OLD NCERT) |
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Four resistance 
are connected so that they form the side of a rectangle AB, BC, CD and DA respectively. Another resistance of 
is connected across the diagonal AC. The equivalent resistance between A and B is
are connected so that they form the side of a rectangle AB, BC, CD and DA respectively. Another resistance of is connected across the diagonal AC. The equivalent resistance between A and B is1. 2Ω
2. 5Ω
3. 7Ω
4. 10Ω
2. 5Ω
3. 7Ω
4. 10Ω
Subtopic: Combination of Resistors |
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The velocity of a particle moving in the x – y plane is given by
and 
Where, t = 0, x = 8 and y = 0, the path of the particle is
and Where, t = 0, x = 8 and y = 0, the path of the particle is
1. A straight line
2. an ellipse
3. a circle
4. a parabola
2. an ellipse
3. a circle
4. a parabola
Subtopic: Speed & Velocity |
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