Electromagnetic Waves — Physics STD 12 Science — Question

A potentiometer circuit shown in the figure is set up to measure e.m.f. of a cell E. As the point P moves from X to Y the galvanometer G shows deflection always in one direction, but the deflection decreases continuously until Y is reached. In order to obtain balance point between X and Y it is necessary to

(a) Decreases the resistance R	(b) Increase the resistance R
(c) Reverse the terminals of battery V	(d) Reverse the terminals of cell E

A proton moving with a velocity, 2.5  , enters a magnetic field of intensity 2.5T making an angle 30°  with the magnetic field. The force on the proton is

(a) 3

(b) 5

(c) 6

(d) 9

If the intensity of the radiation incident on a photo-sensitive plate is doubled, how does the stopping potential change?

 A variable condenser is permanently connected to a 100 V battery. If the capacity is changed from 2μF to 10 μF, then change in energy is equal to

(a) 2

(b) 2.5

(c) 3.5

(d) 4

Assertion : Neutrons penetrate matter more readily as compared to protons.

Reason     : Neutrons are slightly more massive than protons.

(a) If both assertion and reason are true and the reason is the correct explanation of the assertion.

(b) If both assertion and reason are true but reason is not the correct explanation of the assertion.

(c) If assertion is true but reason is false.

(d) If the assertion and reason both are false.

Lines which represent places of constant angle of dip are called

(a) Isobaric lines

(b) Isogonic lines

(c) Isoclinic lines

(d) Isodynamic lines

Two identical parallel plate capacitors are connected in series to a battery of 100 V. A dielectric slab of dielectric constant 4.0 is inserted between the plates of second capacitor.  The potential difference across the capacitors will now be respectively

(a) 50 V, 50 V

(b) 80 V, 20 V

(c) 20 V, 80 V

(d) 75 V, 25 V

A free neutron decays to a proton but a free proton does not decay to a neutron. This is because:

1. Neutron is a composite particle made of a proton and an electron whereas proton is a fundamental particle.
2. Neutron is an uncharged particle whereas proton is a charged particle.
3. Neutron has large rest mass than the proton.
4. Weak forces can operate in a neutron but not in a proton.