Sub-Atomic Particles –Electrons

The video explains how gases conduct electricity under high potential difference and reduced pressure using a discharge tube. It describes the effects of varying pressure on the tube, leading to the discovery of cathode rays. JJ Thomson's experiments revealed that cathode rays are negatively charged particles, later identified as electrons. Thomson measured the charge-to-mass ratio of electrons, while Millikan's oil drop experiment determined the electron's charge. These findings helped establish the fundamental properties of electrons.

What happens inside a discharge tube when the pressure is reduced to 1 millimeter of mercury?

• A spark passes like a flash of light.

• Current starts to flow and a colored glow is observed.

• The glow disappears but the current continues to flow.

• A faint green glow is observed on the glass wall.

Which of the following is NOT a property of cathode rays?

• They travel in straight lines.

• They produce heating effects.

• They carry a positive charge.

• They can penetrate thin materials.

What did JJ Thomson conclude about cathode rays from his experiments?

• They are independent of the gas in the tube.

• They are made of light particles.

• They carry a positive charge.

• They do not produce shadows.

Which factor does NOT affect the deflection of cathode rays in electric and magnetic fields?

• Magnitude of the electron

• Mass of the particle

• Strength of the fields

• Color of the cathode rays

What was the main goal of Millikan's oil drop experiment?

• To observe the behavior of cathode rays

• To determine the charge of an electron

• To study the properties of X-rays

• To measure the mass of an electron

How did Millikan ensure the oil drop remained stationary during his experiment?

• By using a magnetic field

• By adjusting the strength of the electrical field

• By increasing the pressure

• By cooling the oil drop

What was the charge of an electron as determined by Millikan's experiment?

• -1.6 x 10^-19 coulombs

• 1.6 x 10^19 coulombs

• -1.6 x 10^19 coulombs

• 1.6 x 10^-19 coulombs