physics

A radioactive substance has a half-life of 20 hours. What fraction of the original radioactive nuclei will remain after 80 hours?

A. 1/32 B. 1/16 C. 1/8 D. 1/4 E. 1/2 Correct Answer: Option B - 1/16 Explanation 1 → 1/2…

5 years ago

Water does not drip through an open umbrella of silk material unless the inside of the umbrella is touched. Which of the following phenomena is responsible for this?

A. Surface tension B. Hydrostatic upthrust C. Viscosity D. Diffusion E. Osmosis Correct Answer: Option A - Surface tension

5 years ago

Which of the following statements about the atom is/are correct?

I. Energy is needed to remove electrons from an atom II. Particles in the nucleus of an atom are bound…

5 years ago

When the pressure of the gas in a discharge tube is gradually lowered; which of the following are correct?

I. there is a violet glow in the tube II. the glow in the tube splits into bands which get…

5 years ago

Which of the following particles conduct electricity through salty water?

A. Atom B. molecules C. Electrons D. Neutrons E. Ions Correct Answer: Option E - Ions

5 years ago

Which of the following reduce(s) the effect of the back e.m.f. generated in the primary coil of an induction coil?

I.  The capacitor in the circuit II. The make and break contact in the circuit III. The ratio of turns…

5 years ago

How long will it take to heat 3 kg of water from 28°C to 88°C in an electric taking a current of 6 A from an e.m.f. source of 220V?

A. 96s B. 1.20s C. 570s D. 600s E. 1200s Correct Answer: Option C - 570s Explanation Ivt = mcΔθ…

5 years ago

Birds can perch safely on overhead electric power cables without being electrocuted because?

A. birds can withstand high p.d. of the electric power cables B. any accumulated charge on the birds is quickly…

5 years ago