Question 1

Resistance acts to&#10;A) slow down the current drifting in a conductor&#10;B) decrease the current drifting in a conductor&#10;C) increase the current drifting ina conductor&#10;D) limit the current drifting in a conductor

Accepted Answer

Resistance is the opposition offered by a conductor to the flow of current. It limits the current drifting in a conductor by reducing the flow of electrons, thus decreasing the current passing through the conductor.

Question 2

The resistance of a conductor will increase if the&#10;A) length of the conductor is reduced&#10;B) cross-sectional area of the conductor is reduced&#10;C) resistivity of the conductor is reduced&#10;D) the current through the conductor is reduced

Accepted Answer

According to Ohm's law, R = (ρ × L)/A, where R is resistance, ρ is resistivity, L is length, and A is cross-sectional area. It shows that resistance is inversely proportional to the cross-sectional area of the conductor. Therefore, if the cross-sectional area of the conductor is reduced, the resistance of the conductor will increase.

Question 3

Doubling the diameter of a circular conductor will act to&#10;A) double its resistance&#10;B) half its resistance&#10;C) reduce its resistance by a quarter&#10;D) quadruple its resistance

Accepted Answer

Doubling the diameter of a circular conductor increases its cross-sectional area by a factor of four (since area is proportional to the square of the diameter), which reduces its resistance by a quarter, according to the formula for resistance $R = \rho \frac{L}{A}$, where $\rho$ is the resistivity, $L$ is the length, and $A$ is the cross-sectional area.

Question 4

A material's resistivity varies with&#10;A) its length&#10;B) its cross-sectional area&#10;C) its temperature&#10;D) the shape of its cross-section

Accepted Answer

Resistivity is a property of the material and is defined as the resistance of the material per unit length and cross-sectional area. However, it is also dependent on the temperature of the material, which can change its atomic structure, and therefore affect its resistance. Length, cross-sectional area, and shape of the cross-section all affect the resistance of the material, but not the resistivity.

Question 5

The SI unit for resistivity is the&#10;A) ohm&#10;B) ohm per metre&#10;C) ohm metre&#10;D) ohm per cubic metre

Accepted Answer

Resistivity is defined as the resistance of a material of unit length and unit cross-sectional area. Hence, its units are ohm-metre (Ωm) according to the SI system.

Question 6

Halving the current through a conductor will&#10;A) halve its resistance&#10;B) double its resistance&#10;C) quadruple its resistance&#10;D) have no effect on its resistance

Accepted Answer

The resistance of a conductor is determined by its material, length, and cross-sectional area, not by the current flowing through it. Halving the current does not change these physical properties, so it has no effect on the resistance.

Question 7

Increasing the temperature of a pure metal conductor will generally&#10;A) reduce its resistance&#10;B) increase its resistance&#10;C) have no effect on its resistance&#10;D) either a or b

Accepted Answer

Increasing the temperature of a pure metal conductor will increase its resistance due to the increased thermal motion of the metal ions, which increases the likelihood of collisions with electrons and impedes the flow of current. This is known as the temperature coefficient of resistivity.

Question 8

Increasing the temperature of most insulating materials will&#10;A) reduce their resistance&#10;B) increase their resistance&#10;C) have no effect on their resistance&#10;D) either a or b

Accepted Answer

Increasing the temperature of most insulating materials typically reduces their resistance due to increased thermal energy, which allows more charge carriers to move through the material.

Question 9

The 'ohm' is defined in terms of the&#10;A) ratio of voltage to current&#10;B) resisitivity of a material&#10;C) length, cross-sectional area, and resistivity of a conductor&#10;D) the type of conductor

Accepted Answer

The 'ohm' is defined as the ratio of voltage to current, according to Ohm's Law, which states that the current through a conductor between two points is directly proportional to the voltage across the two points.

Question 10

The insulation resistance for a length of cable is 100 megohms. What would be its value if the cable were five times as long?&#10;A) 20 megohms&#10;B) 50 megohms&#10;C) 100 megohms&#10;D) 500 megohms

Accepted Answer

Insulation resistance is directly proportional to the length of the cable. Therefore, if the length of the cable is increased by a factor of 5, the insulation resistance would decrease by a factor of 5. Therefore, the insulation resistance would be 20 megohms (100 megohms/5).

Question 11

The 'a.c. resistance' is of a conductor is __________ than its d.c. resistance, due to a property called __________&#10;A) slightly lower, reactance&#10;B) slightly lower, 'skin effect'&#10;C) slightly higher, reactance&#10;D) slightly higher, 'skin effect'

Accepted Answer

The answer of The 'a.c. resistance' is of a conductor...

Question 12

A.C. resisitance' is caused by a conductor's&#10;A) increase in resistivity due to frequency&#10;B) loss of effective c.s.a. due to frequency&#10;C) increase in collisions between electrons due to frequency&#10;D) increase in temperature due to frequency

Accepted Answer

The answer of A.C. resisitance' is caused by a conductor's&#10;A)...

Deck 4: Resistance