Question 1

An object that has zero resistance is a semiconductor.

Accepted Answer

A semiconductor is a material that has intermediate electrical conductivity between that of a conductor and an insulator. It has a finite resistance, not zero resistance.

Question 2

An atom with fewer electrons than protons is a negative ion.

Accepted Answer

An atom with fewer electrons than protons is actually a positive ion, as it has a net positive charge due to the imbalance of electrons and protons.

Question 3

Current is the opposition to the flow of charge.

Accepted Answer

Current is the flow of electric charge, while resistance is the opposition to the flow of charge.

Question 4

Two charged bodies separated by a distance d exert a repulsive electrical force on each other. The signs of the charges on the two bodies are + and -.

Accepted Answer

Two charged bodies with opposite signs (+ and -) attract each other, not repel.

Question 5

The resistance of a conducting material depends on its composition, length, diameter, and temperature.

Accepted Answer

The resistance of a conducting material is dependent on its composition (resistivity), length, cross-sectional area (diameter), and temperature according to Ohm's law.

Question 6

The SI unit of electric charge is e , the charge on the electron.

Accepted Answer

The SI unit of electric charge is the coulomb (C), which is defined as the amount of charge transported by a constant current of one ampere in one second. The charge on the electron is often given as a fundamental unit of charge, but it is not the SI unit.

Question 7

Solids that are good conductors of heat tend also to be good conductors of electricity.

Accepted Answer

This is because both heat and electricity are transferred through the movement of electrons, and materials that have a high number of free electrons that are able to move easily will conduct both heat and electricity well. Examples of good conductors include metals such as copper, silver, and gold.

Question 8

Larger batteries have higher output voltages.

Accepted Answer

Output voltage is determined by the design of the battery, not necessarily its size or capacity. Larger batteries typically have a higher capacity (measured in amp-hours), but not necessarily a higher output voltage.

Question 9

Electrons are negatively charged.

Accepted Answer

Electrons have a negative charge.

Question 10

Semiconductor technology has been the basis for many new electronic devices.

Accepted Answer

Semiconductor technology has been widely used in the development of various electronic devices such as computers, smartphones, televisions, LED lights, and solar cells, among others.

Question 11

If the length of a wire increases, its resistance decreases.

Accepted Answer

The resistance of a wire is directly proportional to its length. As the length of the wire increases, its resistance also increases.

Question 12

Current is the rate of flow of electric charge.

Accepted Answer

Current is defined as the rate of flow of electric charge per unit time. It is usually measured in amperes (A).

Question 13

Superconductivity is lost when a certain critical temperature is exceeded.

Accepted Answer

This statement is true. Superconductivity occurs at very low temperatures, and as the temperature rises above a critical value, the material will lose its superconducting properties.

Question 14

The resistance of a wire does not change when its temperature changes.

Accepted Answer

The resistance of a wire changes when its temperature changes. As the temperature of the wire increases, the resistance also increases due to an increase in the wire's atomic vibrations, which generates more collisions and impedes the flow of electrons. The relationship between resistance and temperature is given by the formula R2 = R1 (1 + αΔT), where R1 is the initial resistance, R2 is the final resistance, α is the temperature coefficient of resistance, and ΔT is the change in temperature.

Question 15

Voltage is a measure of the energy per unit charge supplied by a battery.

Accepted Answer

This is a correct definition of voltage. Voltage is measured in volts (V) and represents the electric potential difference between two points in a circuit.

Question 16

Voltage can also be called potential.

Accepted Answer

Voltage is often referred to as potential because it represents the electrical potential energy per unit charge at a given point in a circuit.

Question 17

Voltage is the force on a charged object divided by the charge on the object.

Accepted Answer

Voltage is the potential difference between two points and is measured in volts. It represents the work done per unit charge to move a charge between two points, not the force on a charged object divided by the charge on the object.

Question 18

Two charged bodies separated by a distance d exert an electrical force on each other. The distance d is doubled. The electrical force on each body is now 1/2 of the original force.

Accepted Answer

The electrical force between two charged bodies is proportional to the inverse square of the distance between them. If the distance is doubled, the force will decrease by a factor of 1/4 (not 1/2). Therefore, the statement is false.

Question 19

All three types of particles found in atoms are electrically charged.

Accepted Answer

In an atom, neutrons are electrically neutral, while protons are positively charged, and electrons are negatively charged.

Question 20

If the diameter of a wire increases, its resistance decreases.

Accepted Answer

According to the formula for resistance, R = (rho * L) / A, where rho is the resistivity of the material, L is the length of the wire, and A is the cross-sectional area of the wire. As the diameter of the wire increases, the cross-sectional area also increases, and hence the resistance decreases. This is because a larger cross-sectional area means that there is more space for electrons to flow through, reducing the opposition to the flow of current.

Quiz 7: Electricity