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An electron moves in a circle of radius of 1.0cm with a constant speed of 4.0106m/s, electric current at a point on the circle will be: (e=−1.6×10⁻¹⁹C)

Given that the radius of circle R=1.0cm. Speed of electron along the circular path=4.0×106m/s. Constant value of electron or charge... View Article

A bar magnet of magnetic moment M is placed in the magnetic field B. The torque acting on the magnet is:

A pair force is made up of two parallel forces that have the same magnitude but opposing directions and do not have the same path of action. A... View Article

If a wire of resistance R = 10ohm is stretched to double of its length, then new resistance will be:

The expression for the resistance of a wire is given as, R = ρ l/A where, ρ is the resistivity of a material. l is the length of wire.... View Article

Show on a graph, the variation of resistivity with temperature for a typical semiconductor.

The resistivity is given by: ρ=m/ne2τ where n= Number density of electrons τ= Relaxation time With the rise in temperature, the number density... View Article

A particle moves on a circle of radius r with centripetal acceleration as function of time as ac=k²rt² where k is a positive constant .Find the following quantities as a function of time at an instant. (A) The speed of the particle. (B) The tangential acceleration of the particle (C) the resultant acceleration and (D) Angle made by the resultant with tangential direction

Now we know that the magnitude of centripetal acceleration is given by, ac=v2/r where, v is the linear velocity of the particle and r is the... View Article

An atomic power nuclear reactor can deliver 300 MW. The energy released due to fission of each nucleus of uranium atom U²³⁸ is 170 MeV. The number of uranium atoms fissioned per hour will be:-

Nuclear Energy is the energy in the core of an atom. Where an atom is a tiny particle that constitutes every matter in the universe. Normally,... View Article

Five point charges, each of value +q are placed on five vertices of a regular hexagon of side L. What is the magnitude of the force on a point charge of value −q placed at the centre of the hexagon?

Among the five forces on five charges,2pairs (four) of forces are cancelled with each other since they are equal in magnitude and opposite in... View Article

On a 60km track, a train travels the first 30km with a speed of 30kmh−1 . How fast must the train travel the next 30km so as to average 40kmh−1 for the whole trip?

It is given that the first 30km is traveled with the speed 30kmh−1 , let us consider that the speed with which the next 30km is travelled... View Article

The mass of a non-volatile solute of molar mass 40g/mol that should be dissolved in 114g of octane to lower its vapour pressure by 20% is:

The pressure imposed by a gas on a liquid (or solid) in a closed system at a certain temperature is known as vapour pressure. When liquid... View Article

A bullet is fired from a gun, the force on the bullet is given by F=600−2×10⁵t where F is in newton and t in second. The force on the bullet becomes zero as soon as it leaves the barrel. What is the average impulse imparted to a bullet?

Force acting on the bullet is given as ⇒ F=600−2×105t ⇒ t=600/2×105 t = 3×10−3s Now impulse... View Article

A block of mass m = 1kg is placed on a smooth surface and is connected with a spring of constant K = 100N/m and another end of spring is connected to a fixed wall as shown. The block is pulled by a distance A = 0.10 m from its natural length and released at t = 0(A) The maximum speed is after t=π/20s (B) Time taken to cover the first 0.10 m, t=π/20s (C) Time taken to cover the first 0.05 m, t=π/40s (D) Time taken to cover the first 0.05 m, t=π/30s

Given parameters are K = 100N/m m = 1 kg L = 1 m Now, using the formula for the angular frequency of a spring in simple harmonic motion, ω... View Article

A plane electromagnetic wave of frequency 25 MHz travels in free space along the x-direction. At a particular point in space and time, E=6.3 j^V/m. What is Bat this point?

The magnitude of the magnetic field will be given by the magnitude of the electric field divided by the speed of light. From the direction of the... View Article

Consider the situation shown in figure. The wall is smooth but the surface of A and B in contact are rough. The friction on B due to A in equilibrium- (a) is upward (b) is downward (c) is zero (d) the system can’t remain in equilibrium

Here it is given that two blocks A and B who are attached together. From the figure we can see the different forces acting on both the blocks.... View Article

The magnetic induction at a point P which is 4cm distant from a long current carrying wire is 10 −3T. The field of induction at a distance 12 cm from the same current would be?

Magnetic induction, also called electromagnetic induction refers to the production of voltage (or EMF) across an electrical conductor placed... View Article

A body is thrown vertically upwards. Which one of the following graphs correctly represents the velocity vs time?

a) b) c) d) Velocity of a body thrown vertically upwards can be given as: vf= vi+ at where a=−g (always acts in downward direction)... View Article

The maximum emission wavelength at temperature 2000K is 4μm. The maximum wavelength corresponding to temperature 2400K will be

Wien’s law or Wien’s displacement law, named after Wilhelm Wien was derived in the year 1893 which states that black body radiation... View Article

Which of the following velocity-time graph shows a realistic situation for a body in motion :-

Answer: (b) In a practical circumstance, the body cannot have more than one velocity at the same time, or, to put it another way,... View Article

The magnetic field in a travelling electromagnetic wave has a peak value of 20 nT. What is the peak value of electric field strength?

The product of the peak value of the magnetic field and the velocity of light is the peak value of electric field strength. Thus, the value of... View Article

Consider the charges q, q and –q placed at the vertices of the equilateral triangle, as shown in the figure. What is the force on each charge?

The electrostatic force is the electric force that exists between two static and charged particles. Depending on whether the particles are... View Article

A body weighs 72 N on the surface of the earth. What is the gravitational force on it due to the Earth at a height equal to half the radius of the earth? (1) 48 n (2) 32 n (3) 30 n (4) 24 n

Answer: (2) 32N Let's start with the most basic scenario: On the surface of the Earth, i.e., at a height R (where R is the radius of the... View Article

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