The S.I unit for sound energy is

• A. Hz
• B. cd
• C. dB
• D. J

The force per unit charge experienced at a point in a field is the

• A. gravitational field strength
• B. electric potential
• C. electric field intensity
• D. magnetic field strength

An image which cannot be formed on a screen is said to be

• A. inverted
• B. real
• C. virtual
• D. erect

The colours seen in the thin films of oil on the road and in soap bubbles are due to

• A. reflection
• B. interference
• C. diffraction
• D. polarization

A charge of 1.6 x 10^-10C is placed in a uniform electric field of intensity 2.0 x 10⁵NC^-1. What is the magnitude of the electric force exerted on the charge?

• A. 3.2 x10⁵N
• B. 1.8 x10⁵N
• C. 3.2 x10^-5N
• D. 1.8 x10^-5N

An a.c. the generator can be converted to a d.c. generator by replacing the

• A. commutator with an armature
• B. armature with a commutator
• C. commutator with slip rings
• D. slip rings with a commutator

An electron enters perpendicularly into a uniform magnetic field which has a flux density of 0.12 T This results in a magnetic force of 9.6 x 10\(^{-2}\) N on the electron. Calculate the speed of the electron as it enters the magnetic field. (e =1.6 x \(10^{19}\) C)

Iron at 30°C feels colder to the hand than wood at 28°C because

• A. their linear expansivities are not equal.
• B. the temperature of the iron is higher than that of the wood
• C. iron is a better radiator of heat than wood
• D. iron conducts heat more quickly from the hand than wood

An X-ray tube operates at a potential of 2500 V. If the power of the tube is 750 W, calculate the speed of the electron striking the target. [e = 1.6 x 10\(^{-19}\) C; mass of electron = 9.1 x 10\(^{-3}\) kg]

The bob of a simple pendulum takes 8.0s to complete 10 oscillations. Determine the frequency of oscillation of the bob.

• A. 0.125Hz
• B. 1.25Hz
• C. 7.50Hz
• D. 8.00Hz