Correct Answer: A. Red and Violet

Correct Answer: B. 100A

Correct Answer: C. 30°

Correct Answer: C. 4/5 π

Explanation

Phase difference = \(\frac{2\pi x}{\lambda}\)

= \(\frac{2\pi \times 20}{50}\)

= \(\frac{4}{5} \pi\)

Explanation

(a) (i) Neutral point is a point at which the resultant magnetic flux density is zero.

(ii)

(b)(i) (ii) An ammeter is accurate if the current it mea-sures is close to the true value of the current flowing through the instrument.

(c)

The material is surrounded by a thick wall of ferro-magnetic material which does not allow magnetism to pass through them. This shields or protects the material from the earth's magnetic field.

(ii) F = qvBsin\(\theta\) = 1.6 x 10\(^{-19}\) x 2.5 x 10\(^{7}\) x 2 x 0.5 = 4 x 10\(^{2}\) N

(d) Electromagnetic induction laws are

- Whenever there is a change in the magnetic flux linked with a circuit, an e.m.f is induced, the magnitude of which is proportional to the rate of change of the flux linked with the circuit.

- The direction of the induced current is always such as to oppose the change producing it.

Correct Answer: A. 7.2 x 10^-4J

Correct Answer: C. 1.2A

Explanation

P = VI ; I = P/V = 100/250 = 0.4A eachTotal current 3 x 0.4 = 1.2A

Correct Answer: D) a rectifier in an a.c circuit

Explanation

(a)

The experiment is set up as shown in the diagram. The wooden box effective length, I of the string remains constant throughout the experiment. Also the string used is of uniform thickness and must not be changed to ensure that the mass per unit length is constant throughout the experiment. The length of string is tied to the stake at one free end while a known mass is added to the other end. This creates a tension in the string which is equal to the weight of the attached mass. A tuning fork of known frequency is set vibrating and the string is tuned in unison with the fork. The frequency of the fork is recorded. The procedure is repeated by increasing the masses and using different tuning forks four more times. The corresponding tension (weights) and frequency are recorded in a table. Experiment to show that frequency is proportional to the square root of the tension, T. Mathematically, the graph of F against \(\sqrt{T}\) is a straight line through the origin.

(b)(i)

(ii) Second overtone

(c)(i)

(ii)

Correct Answer: B. energy changes occur within the nuclei of atoms

Explanation

Gamma rays are produced in the disintegration of radioactive atomic nuclei and in the decay of certain subatomic particles. Gamma radiation is emitted by excited nuclei or other processes involving subatomic particles; it often accompanies alpha or beta radiation, as a nucleus emitting those particles may be left in an excited (higher-energy) state.