MR 5 - PHYSICS

Four cells each of e.m.f 1.5V and internal resistance of 4Ω are connected in parallel. What is the effective e.m.f. and internal resistance of the combination?

• The effective e.m.f. is 1V and the internal resistance of the combination is 3Ω.
• The effective e.m.f. is 1.5V and the internal resistance of the combination is 1Ω.
• The effective e.m.f. is 2V and the internal resistance of the combination is 2Ω.
• The effective e.m.f. is 2.5V and the internal resistance of the combination is 0.5Ω.

Steel is more suitable for permanent magnet than iron because the former

• is easily demagnetized by shaing vigorously

• is an alloy of many metals

• is easily magnetized by alternating current through one cycle

• retains magnetism more than iron

Which of the following electromagnetic waves is least energetic?

• Infra-red rays

• X-rays

• Ultra-violet rays

• Gamma rays

Which of the following statements is true about an astronomical telescope?

• The focal length of the objective lens is longer than that of the eyepiece

• The final image is at the near point of the eye

• The final image is at infinity

• The eye is accommodated

A 3000W electric cooker is to be used on a 200V mains circuit. Which of the fuses below can be used safely with the cooker?

• 2A

• 5A

• 10A

• 20A