Insulators, Conductors, Semiconductors, and Superconductors

When a metal plate is given a positive charge, which of the following is taking place?

• Protons (positive charges) are transferred to the plate from another object.

• Electrons (negative charges) are transferred from the plate to another object.

• Electrons (negative charges) are transferred from the plate to another object, and protons (positive charges) are also transferred to the plate from another object.

• It depends on whether the object conveying the charge is a conductor or an insulator.

Which one of these systems has the most negative charge?

• 2 electrons

• 3 electrons and 1 proton

• 5 electrons and 5 protons

• N electrons and N -3 protons

• 1 electron

Two protons placed near one another with no other objects close by would

• accelerate away from each other.

• remain motionless.

• accelerate toward each other.

• be pulled together at constant speed.

• move away from each other at constant speed.

One way to change a neutral metallic object with a negative charge is to do one of the following:

• Add some electrons

• Cut out a part of the object

• Remove some electrons

• Add some neutral atoms

Which of the following statements is true about superconductors?

• superconductors have zero resistance.

• Most materials have critical temperature between zero Kelvin and 10 Kelvin.

• A material can become superconductor when its temperature drops below the material's critical temperature.

• All of the above.

A student performed an experiment to find the conductivity of some material. Which piece of data tells him that this material is a superconductor?

• R=10^6 Ω

• R=1600Ω

• R=0Ω

• R=10^-2 Ω

Why is the copper wire protected using insulating rubber?

• Insulating rubber allows the charges to be conducted away from the copper wire.

• Insulating rubber conducts electricity, allowing the cable to carry more charges.

• Insulating rubber stops other conducting materials from touching the wire, keeping the charges in the copper wire.

• Insulating rubber has more free electrons than the copper wire.

What happens to the conductivity of distilled water when you dissolve table salt in it?

• Increases

• Stays the same

• Decreases

• None of the above

Which of the following are materials that have zero resistance to the conduction of electricity?

• Insulators

• Semiconductors

• Conductors

• Superconductors

Which of the following statements is correct about electrical conductivity?

• Electrical resistance of superconductors is zero at very low temperatures.

• Insulators have low electrical resistance.

• Metals are bad conductors of electricity.

• Silicon and germanium are examples of superconductors.