Physics-

#### Five lumen/watt is the luminous efficiency of a lamp and its luminous intensity is 35 candela. The power of the lamp is

Physics-General

- 36 W
- 88 W
- 80 W
- 176 W

#### Answer:The correct answer is: 88 WEfficiency of light source

..... (i)

and ..... (ii)

From equation (i) and (ii)

.

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#### Lux is equal to

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#### A lamp rated at 100 cd hangs over the middle of a round table with diameter 3 m at a height of 2 m. It is replaced by a lamp of 25 cd and the distance to the table is changed so that the illumination at the centre of the table remains as before. The illumination at edge of the table becomes X times the original. Then X is

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#### The maximum kinetic energy (E_{k} ) of emitted photoelectrons against frequency v of incident radiation is plotted as shown in fig The slope of the graph is equal to

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#### If f(x) is a polynomial of degree five with leading coefficient one such that f(1)=1^{2},f(2)=2^{2},f(3)=3^{2},f(4)=4^{2},f(5)=5^{2} then

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#### If f(x) = ax^{2}+ bx + c such that f(p) + f(q) = 0 where a0 ; p , qR then number of real roots of equation f(x) = 0in interval [p, q] is

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f(p)=–f(q) eitherf(p)f(q)<0 or f(p) =0=f(q)

exactlyonerootin(p,q) orrootsarepandq

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#### If f(x) is a differentiable function satisfying f(x+ y)= f(x)f(y) x, y R and f'(0)=2 then f(x)=

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#### In the following diagram if then

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#### Maximum kinetic energy (E_{k} ) of a photoelectron varies with the frequency ( v ) of the incident radiation as

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#### Three rods of same dimensions are arranged as shown in figure. They have thermal conductivities and . The points and are maintained at different temperatures for the heat to flow at the same rate along and then which of the following options is correct

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It is given that

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#### Three rods of same dimensions are arranged as shown in figure. They have thermal conductivities and . The points and are maintained at different temperatures for the heat to flow at the same rate along and then which of the following options is correct

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The given arrangement of rods can be redrawn as follows

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#### Which of the curves in figure represents the relation between Celsius and Fahrenheit temperatures

Hence graph between and will be a straight line with positive slope and negative intercept

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Hence graph between and will be a straight line with positive slope and negative intercept

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#### Two circular discs A and B with equal radii are blackened. They are heated to some temperature and are cooled under identical conditions. What inference do you draw from their cooling curves?

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Where c is specific heat of material.

or

rate of cooling varies inversely as specific heat. From the graph, for A rate of cooling is larger. Therefore, specific heat of A is smaller.

Where c is specific heat of material.

or

rate of cooling varies inversely as specific heat. From the graph, for A rate of cooling is larger. Therefore, specific heat of A is smaller.

#### Two circular discs A and B with equal radii are blackened. They are heated to some temperature and are cooled under identical conditions. What inference do you draw from their cooling curves?

physics-General

According to Newton’s law of cooling, rate of cooling is given by

Where c is specific heat of material.

or

rate of cooling varies inversely as specific heat. From the graph, for A rate of cooling is larger. Therefore, specific heat of A is smaller.

Where c is specific heat of material.

or

rate of cooling varies inversely as specific heat. From the graph, for A rate of cooling is larger. Therefore, specific heat of A is smaller.