Question 1

Consider some material that has been cooled until it has become a superconductor.If it is cooled even further its resistance will:

Accepted Answer

Once a material becomes a superconductor, its resistance drops to zero. Cooling it further won't change its resistance, as it cannot be less than zero. However, none of the provided options accurately describe this scenario, making "None of the above" the correct choice.

Question 2

A 7.00-Ω resistor is dissipating 70.0 watts.What are the current through it and the potential difference across it?

Accepted Answer

We can use the formula for power, P = I^2*R, where P is power, I is current, and R is resistance.

Using this formula, we can rearrange it to solve for current:

I = sqrt(P/R)

Plugging in the values given in the problem, we get:

I = sqrt(70/7) = sqrt(10) = 3.16 A

To find the potential difference (voltage) across the resistor, we can use another formula:

V = I*R

Plugging in the values, we get:

V = 3.16*7 = 22.1 V

Therefore, the correct choice is C, with a current of 3.16 A and a potential difference of 22.1 V.

Question 3

When the voltage across a nonohmic resistor is doubled,the current through it triples.What happens to the power delivered to this resistor?

Accepted Answer

The power delivered to a resistor is given by $P = IV$, where $I$ is the current and $V$ is the voltage. If the voltage is doubled and the current triples, the new power is $P_{new} = 3I \times 2V = 6IV$, which is 6 times the original power.

Question 4

Resistor A has twice the resistance of resistor B.When individually connected across a given potential difference,which one dissipates the most power;and when connected in series across the same potential difference,which one dissipates the most power?

Accepted Answer

When resistors are connected individually across a potential difference, the power dissipated is given by $P = \frac{V^2}{R}$, where $V$ is the potential difference and $R$ is the resistance. Since resistor A has twice the resistance of resistor B, it will dissipate less power individually due to the inverse relationship between power and resistance. When connected in series, the total voltage drop across resistor A will be higher because it has a higher resistance (voltage drop across a resistor in a series circuit is directly proportional to its resistance), leading to more power dissipation in resistor A according to $P = \frac{V^2}{R}$ or $P = I^2R$, where $I$ is the current through the resistor.

Question 5

A superconducting wire's chief characteristic is which of the following?

Accepted Answer

The chief characteristic of a superconducting wire is that it has no resistance, allowing for the flow of electric current with high efficiency.

Question 6

Superconductivity was discovered by:

Accepted Answer

Superconductivity was discovered by Heike Kamerlingh Onnes in 1911 through his experiments on the resistance of mercury.

Question 7

When a superconductor's temperature drops below the critical temperature,its resistance:

Accepted Answer

When a superconductor's temperature drops below the critical temperature, its resistance drops to zero, allowing for an efficient flow of electric current without any loss of energy due to resistance.

Question 8

Some superconductors are capable of carrying a very large quantity of current.If the measured current is 3.00 × 10⁶ A,how many electrons are moving through the superconductor per second? (e = 1.60 × 10−¹⁹ C)

Accepted Answer

The answer of Some superconductors are capable of carrying a...

Question 9

When current is flowing in a superconductor,which statement is not true?

Accepted Answer

In a superconductor, no external energy is required to maintain the flow of current, so a battery is not needed. This is one of the unique characteristics of superconductivity.

Question 10

A light bulb with a tungsten filament is attached to a source of variable voltage.As the voltage is increased on the bulb,

Accepted Answer

As the voltage is increased on the bulb, the temperature of the tungsten filament increases, which causes an increase in the resistance of the bulb. This ultimately leads to an increase in the power dissipated as well. Ohm's law states that I = V/R, so if the resistance increases with the voltage, the current will decrease. Therefore, choice B is the best answer. Choice A is incorrect because the resistance of the bulb increases, not decreases. Choice C is also incorrect because when the resistance increases, the current in the bulb decreases, not increases. Choice D is also incorrect because the power dissipated will increase as the voltage and resistance increase.

Quiz 17: Current and Resistance