Electric Charges and Fields — Physics STD 12 Science — Question

A dimensionless quantity:

1. Never has a unit.
2. Always has a unit
3. May have a unit.
4. Does not exist.

A point charge is brought in an electric field. The electric field at a nearby point.

The magnetic moment of a circular coil carrying current is:

The internal resistance of a cell depends on(a) The distance between the plates(b) The area of the plates immersed(c) The concentration of the electrolyte(d) All the above

In a transistor, a change of 8.0 mA in the emitter current produces a change of 7.8 mA in the collector current. What change in the base current is necessary to produce the same change in the collector current(a) 50 mA(b) 100 mA(c) 150 mA(d) 200 mA

The angle of dip at a place is 60°. At this place the total intensity of earth's magnetic field is 0.64 units. The horizontal intensity of earth's magnetic field at this place is(a) 1.28 units(b) 0.64 units(c) 0.16 units(d) 0.32 units

Consider the diffraction patern for a small pinhole. As the size of the hole is increased:

When there is an electric current through a conducting wire along its length, then an electric field must exist(a)  Outside the wire but normal to it(b) Outside the wire but parallel to it(c) Inside the wire but parallel to it(d) Inside the wire but normal to it

A uniform magnetic field acts at right angles to the direction of motion of electrons. As a result, the electron moves in a circular path of  radius 2 cm. If the speed of the electrons is doubled, then the radius of the circular path will be(a) 2.0 cm(b) 0.5 cm(c) 4.0 cm(d) 1.0 cm