Archives

Three charges q, q and q are placed at the vertices of an equilateral triangle of side l as shown in the figure. if the net electrostatic energy of the system is zero, then q is equal to

Electric potential energy is possessed by an object by the virtue of two elements, those being, the charge possessed by an object itself and the... View Article

Consider a uniform square plate of side a and mass m. The moment of inertia of this plate about an axis perpendicular to its plane and passing through one of its corner is:

We can easily find R using the Pythagoras theorem, ⇒R=√ a2−(a/2)2 =a√2 We know that for a square plate, the moment of inertia along a... View Article

The value of acceleration due to gravity ′g′, at earth’s surface is 10m/s2. Its value at the centre of the earth which is assumed to be sphere of radius ′R′ and uniform mass density, is

There is no mass at exact center of Earth to provide a gravitational pull and thus a gravitational acceleration⇒acceleration due to gravity GM/r2... View Article

A proton, a deuteron and an α-particle are projected perpendicular to the direction of a uniform magnetic field with same kinetic energy. The ratio of the radii of the circular paths described by them is

Radius of circular path r = mv/Bq Using p = mv = √2mK where K is the kinetic energy of the particle. We get r = √2mK/Bq ⟹ r ∝ √m/q Given :... View Article

Friction does not depend on the nature of the surface in contact.

The frictional force works to inhibit relative motion between two surfaces when they are in contact. The body can move relative to the surface... View Article

Let ar and at represent radial and tangential acceleration . the motion of particle may be circular if : ( assume that only momentary rest is allowed) A. ar = at = 0 B. ar = 0 and at≠0 C. ar ≠ 0 and at=0 D.ar≠ 0 and at≠0

Tangential acceleration is the reason of a particle travelling faster or slower in a circular motion. A uniform motion is one in which the... View Article

Two circular, similar, coaxial loops carry equal currents in the same direction. If the loops are brought nearer, what will happen?

Answer: Current will decrease in each loop The flux between the two loops rises as they are brought closer. According to Lenz's law, a... View Article

The displacement of a particle is given by x=(t−2)2 where x is in metres and t is in seconds. The distance covered by the particle in first 4 seconds is

The distance travelled is given by x=(t−2)2 = t2–4t+4 As velocity is given by v = dx/dt v=2t−4 Distance covered=∫∣v∣dt =∣t2–4t∣ =4t−t2 for... View Article

A body revolves with constant speed v in a circular path of radius r . the magnitude of its average acceleration during motion between two points in diametrically opposite direction is:

The acceleration will change as there is change in the velocity at any direction.Speed of the body is given to be constant. At diametrically... View Article

A charge q is placed at every corner of a square having side a. how much charge must be placed at its centre to bring the system in equilibrium?

Let the side length of the square be a. In △ACD, ⇒AD2 + CD2 = AC2 ⇒ a2 + a2 =AC2 (AC=√2a) However, OC = AC/2 = a/√2 Because of the... View Article

The minimum and maximum distances of a satellite from the centre of the Earth are 2R and 4R respectively, where R is the radius of Earth and M is the Earth. The radius of curvature at the point of minimum distance is

Using angular momentum conservation, which implies that any of the individual angular momenta can vary as long as the aggregate remains constant.... View Article

A charged particle of mass m and charge q is released from rest in an electric field of constant magnitude E. The kinetic energy of the particle after time t is

Newton’s all three laws of motion are very important for the questions in which objects falling from a particular height for a particular time... View Article

The ratio of escape velocity at earth ve to the escape velocity at a planet vp whose radius and mean density are twice as that of earth is:

Escape velocity is an initial velocity at which, a body when thrown will leave the gravitational field of earth and never come back and its... View Article

In a current carrying load solenoid, the magnetic field produced does not depend upon

A solenoid is a common term for a wire coil used as an electromagnet. It also applies to any system that uses a solenoid to transform electric... View Article

A uniform sphere of mass 500 g rolls without slipping on a plane surface so that its centre moves at a speed of 0.02 m/s . The total kinetic energy of rolling sphere would be (in J)

Consider v to be the velocity of the sphere's centre. When rolling without sliding, the angular speed of the centre is equal to vr, where r is... View Article

A current of 1.40 ampere is passed through 500mL of 0.180M solution of zinc sulphate for 200 seconds. The molarity of Zn2+ ions after deposition of zinc is:

The equation is given by Zn2++ 2e− ⟶ Zn Faraday = Charge/96500 =1.40×200/96500 = 2.90×10−3 mol ∴Zn deposited =2.90×10−3/2 =1.45×10−3 mol Now,... View Article

Two resistors whose value are in ratio 2:1 are connected in parallel with one cell. Then ratio of power dissipated is

The heat developed is given by H = V2t/R ⇒ HHalf/Hfull = (RFull/RHalf) = R/R/2 = 2 Therefore, HHalf = 2 × HFull... View Article

A conducting rod of length l is hinged at point O. It is free to rotate in a vertical plane. There exists a uniform magnetic field B in horizontal direction. The rod is released from the position. What is the potential difference between the two ends of the rod is proportional to?

The gravitational potential decreases to increase the kinetic energy of the rod. The equation can be written as, mg 1/2sinθ =... View Article

The angle of dip at a place is δ. If the dip is measured in a plane making an angle θ with the magnetic meridian, the apparent angle of dip δ1 will be :

Let δ1 be the angle of dip when dip circle is in magnetic meridian tanδ1=V/H The dip circle when makes an... View Article

A photoelectric cell is illuminated by a point source of light 1m away. What happens when the source is shifted to 2m?

The intensity of light is exactly proportional to the number of photoelectrons released each second. The light source's intensity is I = 1/d2... View Article

M	T	W	T	F	S	S
					1	2
3	4	5	6	7	8	9
10	11	12	13	14	15	16
17	18	19	20	21	22	23
24	25	26	27	28	29	30
31