In case of double insulated hair dryer there is great need of earth wire because the case of it is made of a conducting material .

A device called a toroid (figure) is often used to create an almost uniform magetic fiedl in some enclosed area. The device consists of a conducting wire wraped around a ring (a torus) made of a non conducting material. For a toroid having N closely spaced turns of wire, calculate the magnetic field in the region occupied by the torus, a distasnce r from the centre.

Consider an evacuated cylindrical chamber of height h having rigid conducting plates at the ends and an insulating curved surface as shown in the figure. A number of spherical balls made of a light weight and soft material and coated with a conducting material are placed on the bottom plate. The balls have a radius r lt lt h . Now, a high voltage source (HV) is connected across the conducting plates such that the bottom plate is at +V_0 and the top plate at -V_0 . Due to their conducting surface, the balls will get charged, will become equipotential with the plate and are repelled by it. The balls will eventually collide with the top plate, where the coefficient of restitution can be taken to be zero due to be soft nature of the material of the balls. The electric field in the chamber can be considered to be that of a parallel plate capacitor. Assume that there are no collisions between the balls and the interaction between them is negligible. (Ignore gravity) Which one of the following statements is correct ?

Consider an evacuated cylindrical chamber of height h having rigid conducting plates at the ends and an insulating curved surface as shown in the figure. A number of spherical balls made of a light weight and soft material and coated with a conducting material are placed on the bottom plate. The balls have a radius r lt lt h . Now, a high voltage source (HV) is connected across the conducting plates such that the bottom plate is at +V_0 and the top plate at -V_0 . Due to their conducting surface, the balls will get charged, will become equipotential with the plate and are repelled by it. The balls will eventually collide with the top plate, where the coefficient of restitution can be taken to be zero due to be soft nature of the material of the balls. The electric field in the chamber can be considered to be that of a parallel plate capacitor. Assume that there are no collisions between the balls and the interaction between them is negligible. (Ignore gravity) The average current in the steady state registered by the ammeter in the circuit will be

A coil one turn is made of a wire of certain lenghth and then from the same length a coil of two turns is made. If the same current is passed both the cases, then the ratio of magnetic induction at there centres will be

A mass m is suspended from a wire . Change in length of the wire is Deltal . Now the same wire is stretched to double its length and the same mass is suspended from the wire. The change in length in this case will become (it is suspended that elongation in the wire is within the proportional limit)

A mass m is suspended from a wire . Change in length of the wire is Deltal . Now the same wire is stretched to double its length and the same mass is suspended from the wire. The change in length in this case will become (it is suspended that elongation in the wire is within the proportional limit)

In the following diagram , the length of wires AB and BC are equal but the radius of wire AB is double that of BC. The ratio of potential gradient on wires AB and BC will be ( wire are made of same material).

A hollow cube A of very small thickness at temperature T emits radiation like a black body. The cube A is kept in a room of temperatue T_(0)(ltT) . The side of cube is doubled without changing the volume of material and its temperature. Find the ratio of rate of cooling of cube A in first case to that of second case.

Assertion: A positively charged rod is held near a neutral conducting solid sphere as illustrated below. The sphere lies on a insulated stand. The potential of ground (or earth) is zero. The potential at point A (point A need not be centre of the sphere) is higher compared to potential of gound (earth). Reason: In this situation of assertion, the potential at the centre of conducting sphere is positive. the solid sphere being conducting, potential at each point in the sphere is same.

Assertion: A positively charged rod is held near a neutral conducting solid sphere as illustrated below. The sphere lies on a insulated stand. The potential of ground (or earth) is zero. The potential at point A (point A need not be centre of the sphere) is higher compared to potential of gound (earth). Reason: In this situation of assertion, the potential at the centre of conducting sphere is positive. the solid sphere being conducting, potential at each point in the sphere is same.