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State two circumstances when one may get an electric shock from an electric gadget. What preventive measure must be provided with the gadget to avoid it?

At the time of short circuit, the current in the circuit

(a) reduces substantially

(b) does not change

(c) increases heavily

(d) vary continuously

A clear transparent glass sphere $(\mu =1.5)$ of radius $R$ is immersed in a liquid of refractive index $1.25$. A parallel beam of light incident on it will converge to a point. The position of this point measured from the centre of the sphere will be

In the above figure, the parallel rays meet/appear to meet ___.

A $10\text{mm}$ long awl pin is placed vertically in front of a concave mirror. A $5\text{mm}$ long image of the awl pin is formed at $30\text{cm}$ in front of the mirror. The focal length of this mirror is:

The sensation of seeing an object remains for about _____ of a second after the object is removed from the view.

Which of the following conducts electricity

[AFMC 1995]

The ability of an eye to adjust its focal length by itself to see nearby and distant objects is called as ______________.

A battery of e.m.f. 15 V and internal resistance $3\Omega$ is connected to two resistors $3\Omega$ and $6\Omega$ connected in parallel. Find:

(a) the current through the battery,

(b) the p.d. between the terminals of the battery,

(c) the current in $3\Omega$ resistor,

(d) the current in $6\Omega$ resistor.

In a condenser, water enters at ${30}^{\circ }C$ and flows at the rate 1500 kg/hr. The condensing steam is at a temperature of ${120}^{\circ }C$ and cooling water leaves the condenser at ${80}^{\circ }C$. Specific heat of water is 4.187 kJ/kgK. If the overall heat transfer coefficient is 2000 W/m${}^2$K, the heat transfer area is

Amplitude of an oscillator reduces to one fourth of its initial value when it completes 200 oscillations. What will be its amplitude, when it completes 400 oscillations.

Name two electromagnetic waves of wavelength smaller than that of violet light. State one use of each.

If the length of a copper wire is increased by $5\%$ due to stretching. What will be the percentage increase in its resistance?

The escape velocity from the earth is $11\text{km/s}$. The escape velocity from a planet having twice the radius and same density as that of the earth is (in $\text{km/s}$)

A copper block of mass $2.5\text{kg}$ is heated in a furnace to a temperature of ${500}^{\circ }C$ and then placed on large ice block. The maximum amount of ice that can melt is (Specific heat of copper $=0.39{\text{Jg}}^{-1}{}^{\circ }{C}^{-1}$, latent heat of fusion of water $=335{\text{Jg}}^{–1})$

A light ray passes through the poles of all the four lenses given in the options individually. Through which lens will the deviation of the light ray from its original path be maximum?

The phenomenon of light hitting a surface and then bouncing off is termed as ___ .

Why are the roof and the walls of an auditorium covered with sound-absorbing materials?

The magnifying power of a telescope is $9$. When it is adjusted for parallel rays, the distance between the objective and the eye-piece is found to be $20\text{cm}$. The focal lengths of the lenses are

The sound which is below the frequency of 20 Hz is called _______.

The refractive indices of four media A, B, C and D are 1.44, 1.52, 1.65 and 1.36 respectively. When light travelling in air is incident in these media at equal angles, the angle of refraction will be the minimum : (a) in medium A (b) in medium B (c) in medium C (d) in medium D

Why is that parabolic mirrors are used instead of spherical mirrors in real life situations?

In a given ammeter, a student sees that a needle indicates 17 divisions in ammeter while performing an experiment to verify Ohm's law. If ammeter has 10 divisions between 0 and 0.5A, the what is the value corresponding to 17 divisions.

1. 512

If the mass of earth were $4$ times the present mass, the mass of the moon were half the present mass and the moon was revolving round the earth at twice the present distance, the time period of revolving of the moon would be (in days)

(Take the normal time period of moon be $28$ days)

A plane has a take-off speed of $120m{s}^{-1}$ after covering a distance of $2400m$. Determine the acceleration $\left(a\right)$ of the plane (assuming it to be constant) and the time $\left(t\right)$ required to reach that speed.

If a change in current of 0.01 A in one coil produces a change in magnetic flux of $2\times {10}^{-2}$ Wb in the other coil, then the mutual inductance (in henry) of the two coils is

In an aluminum $\left(Al\right)$ bar of square cross section, a square hole is drilled and is filled with iron $\left(Fe\right)$ as shown in the figure. The electrical resistivities of Al and Fe are $2.7\times {10}^{-8}\Omega -m$ and $1.0\times {10}^{-7}\Omega -m$, respectively. The electrical resistance between the two faces $P$ and $Q$ of the composite bar is

What are the three forms of water?

A reversible heat engine receives $2kJ$ of heat from a reservoir at $1000K$ and a certain amount of heat to a reservoir at $400K$. The net work ouput (in$kJ$) of the cycle is

The blue colour of the sky is due to the ___ .

(a) At what voltage is the electric power from the generating station transmitted? Give a reason for your answer.

(b) What is the nature of the current transmitted from the power station?

‘Being a rookie’ means ________________