Question 1

Household 120-V outlets are made to accept three-pronged plugs. One of the prongs attaches to the "live" wire at 120 V, and another attaches to the "neutral" wire that is connected to ground. What is the round third prong for?

Accepted Answer

The third prong is a grounding prong that connects the case of the appliance directly to ground, providing a path for electrical current to safely dissipate in case of a fault, thus enhancing safety.

Question 2

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 increases, the filament's temperature rises, causing its resistance to increase due to the positive temperature coefficient of resistance of tungsten.

Question 3

A certain material is in a room at 27°C. If the absolute temperature (K) of the material is tripled, its resistance quadruples. (Water freezes at 273 K.) What is the value for $\alpha$, the temperature coefficient of resistivity?

Accepted Answer

The temperature coefficient of resistivity is given by:$$\alpha = \frac{1}{R}\frac{dR}{dT}$$where R is the resistance and T is the temperature.In this problem, the resistance quadruples when the absolute temperature triples. Therefore, we have:$$\frac{R_2}{R_1} = 4$$and$$\frac{T_2}{T_1} = 3$$Substituting these values into the equation for the temperature coefficient of resistivity, we get:$$\alpha = \frac{1}{4}\frac{dR}{dT} = \frac{1}{4}\frac{R_2 - R_1}{T_2 - T_1} = \frac{1}{4}\frac{3R_1}{2T_1} = \frac{3}{8}\frac{R_1}{T_1}$$Since the material is at 27°C, we have:$$T_1 = 27°C + 273 K = 300 K$$Substituting this value into the equation for the temperature coefficient of resistivity, we get:$$\alpha = \frac{3}{8}\frac{R_1}{T_1} = \frac{3}{8}\frac{R_1}{300 K} = 0.0025 (°C)^{-1}$$Therefore, the correct answer is B.

Question 4

A hair dryer draws 1500 W, a curling iron draws 800 W, and an electric light fixture draws 500 W. If all three of these appliances are operating in parallel on a 120 V circuit, what is the total current drawn?

Accepted Answer

The answer of A hair dryer draws 1500 W, a...

Question 5

Carbon has a negative temperature coefficient of resistance of -0.5 *10^-3 (°C) ^- ¹. What temperature increase would result in a resistance decrease of 3% for a carbon resistor?

Accepted Answer

The resistance change percentage is given by the formula: ΔR/R = α * ΔT. Here, ΔR/R = -0.03 (for a 3% decrease), and α = -0.5 x 10^-3. Solving for ΔT gives ΔT = 60°C.

Question 6

What is the maximum number of 60-W light bulbs you can connect in parallel in a 120-V home circuit without tripping the 20-A circuit breaker?

Accepted Answer

The answer of What is the maximum number of 60-W...

Question 7

A metal wire has a resistance of 25.00 $\Omega$ under room temperature conditions of 25°C. When the wire is heated to 85°C the resistance increases by 1.95 $\Omega$. What is the temperature coefficient of resistivity of this metal?

Accepted Answer

The temperature coefficient of resistivity (α) is calculated using the formula: α = ΔR / (R₀ * ΔT), where ΔR is the change in resistance, R₀ is the original resistance, and ΔT is the change in temperature. Here, ΔR = 1.95 Ω, R₀ = 25.00 Ω, and ΔT = 85°C - 25°C = 60°C. Substituting these values gives α = 1.95 / (25 * 60) = 1.3 × 10⁻³ (°C)⁻¹.

Question 8

The resistance of a platinum wire is to be calibrated for low-temperature work. A platinum wire with resistance 2.000 $\Omega$ at 20°C is immersed in liquid nitrogen at 77 K (-196°C). If the temperature response of the platinum wire is linear, what is the expected resistance of the platinum wire at -0196°C? [$\alpha$_platinum= 3.92 *10^-³ (°C)^-¹].

Accepted Answer

The answer of The resistance of a platinum wire is...

Question 9

A metal wire has a resistance of 10.00 $\Omega$ at a temperature of 20.0°C. If the same wire has a resistance of 10.55 $\Omega$ at 90°C, what is the resistance when its temperature is 0.0°C?

Accepted Answer

The resistance of a metal wire increases with increasing temperature. The temperature coefficient of resistance is given by:$$\alpha = \frac{R_2 - R_1}{R_1(T_2 - T_1)}$$where $R_1$ and $R_2$ are the resistances at temperatures $T_1$ and $T_2$, respectively.In this problem, we have:$R_1 = 10.00 \Omega$$R_2 = 10.55 \Omega$$T_1 = 20.0°C$$T_2 = 90°C$Substituting these values into the equation above, we get:$$\alpha = \frac{10.55 \Omega - 10.00 \Omega}{10.00 \Omega(90°C - 20°C)} = 0.0045°C^{-1}$$Now, we can use the equation:$$R_3 = R_1[1 + \alpha(T_3 - T_1)]$$to find the resistance at $T_3 = 0.0°C$.Substituting the values we know into this equation, we get:$$R_3 = 10.00 \Omega[1 + 0.0045°C^{-1}(0.0°C - 20°C)] = 9.84 \Omega$$Therefore, the correct answer is C) 9.84 \Omega.

Question 10

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

Accepted Answer

A superconducting wire's chief characteristic is its lack of resistance.

Question 11

A tungsten wire is used to determine the melting point of indium. The resistance of the tungsten wire is 6.000 $\Omega$ at 20°C and increases to 9.700 $\Omega$ as the indium starts to melt. $\alpha$_tungsten = 4.50 * 10 ^- ³ (°C) ^- ¹. What is the melting temperature of indium?

Accepted Answer

The change in resistance can be used to calculate the temperature change using the formula: R = R0(1 + αΔT). Solving for ΔT gives ΔT = (R/R0 - 1)/α. Substituting the given values: ΔT = (9.700/6.000 - 1)/(4.50 × 10^-3) = 137°C. Adding this to the initial temperature (20°C) gives the melting point of indium as 157°C.

Question 12

A 22-$\Omega$ platinum wire at 20°C with a temperature coefficient of resistivity of 3.9 *10 ^- ³ (°C) ^- ¹ will have what resistance at 100°C?

Accepted Answer

The resistance of a wire is given by the equation:R = ρL/Awhere:R is the resistance in ohmsρ is the resistivity in ohm-metersL is the length of the wire in metersA is the cross-sectional area of the wire in square metersThe temperature coefficient of resistivity is given by the equation:α = (1/ρ)(dρ/dT)where:α is the temperature coefficient of resistivity in 1/°Cρ is the resistivity in ohm-metersT is the temperature in °CThe change in resistance due to a change in temperature is given by the equation:ΔR = RαΔTwhere:ΔR is the change in resistance in ohmsR is the original resistance in ohmsα is the temperature coefficient of resistivity in 1/°CΔT is the change in temperature in °CIn this problem, we have:R = 22 ohmsρ = 1.68 × 10^-8 ohm-metersL = 1 meterA = 1 × 10^-6 square metersα = 3.9 × 10^-3 1/°CΔT = 100°C - 20°C = 80°CPlugging these values into the equations above, we get:ΔR = (22 ohms)(3.9 × 10^-3 1/°C)(80°C) = 6.64 ohmsR + ΔR = 22 ohms + 6.64 ohms = 28.64 ohmsTherefore, the resistance of the wire at 100°C will be 28.64 ohms, which is closest to choice A, 29 ohms.

Question 13

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.

Question 14

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

Accepted Answer

In a superconducting state, the material has zero electrical resistance. Cooling it further does not change this zero resistance, so none of the choices accurately describe the change in resistance.

Question 15

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

Accepted Answer

In a superconductor, once the current is established, it can continue indefinitely without a battery because there is no resistance.

Quiz 19: Electric Currents and Circuits

Household 120-V outlets are made to accept three-pronged plugs. One of the prongs attaches to the "live" wire at 120 V, and another attaches to the "neutral" wire that is connected to ground. What is the round third prong for?

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

A certain material is in a room at 27°C. If the absolute temperature (K) of the material is tripled, its resistance quadruples. (Water freezes at 273 K.) What is the value for $\alpha$ , the temperature coefficient of resistivity?

A hair dryer draws 1500 W, a curling iron draws 800 W, and an electric light fixture draws 500 W. If all three of these appliances are operating in parallel on a 120 V circuit, what is the total current drawn?

Carbon has a negative temperature coefficient of resistance of -0.5 *10^-3 (°C) ^- ¹. What temperature increase would result in a resistance decrease of 3% for a carbon resistor?

What is the maximum number of 60-W light bulbs you can connect in parallel in a 120-V home circuit without tripping the 20-A circuit breaker?

A metal wire has a resistance of 25.00 $\Omega$ under room temperature conditions of 25°C. When the wire is heated to 85°C the resistance increases by 1.95 $\Omega$ . What is the temperature coefficient of resistivity of this metal?

A metal wire has a resistance of 10.00 $\Omega$ at a temperature of 20.0°C. If the same wire has a resistance of 10.55 $\Omega$ at 90°C, what is the resistance when its temperature is 0.0°C?

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

A tungsten wire is used to determine the melting point of indium. The resistance of the tungsten wire is 6.000 $\Omega$ at 20°C and increases to 9.700 $\Omega$ as the indium starts to melt. $\alpha$ _tungsten = 4.50 * 10 ^- ³ (°C) ^- ¹. What is the melting temperature of indium?

A 22- $\Omega$ platinum wire at 20°C with a temperature coefficient of resistivity of 3.9 *10 ^- ³ (°C) ^- ¹ will have what resistance at 100°C?

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

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

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

Quiz 19: Electric Currents and Circuits

Household 120-V outlets are made to accept three-pronged plugs. One of the prongs attaches to the "live" wire at 120 V, and another attaches to the "neutral" wire that is connected to ground. What is the round third prong for?

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

A certain material is in a room at 27°C. If the absolute temperature (K) of the material is tripled, its resistance quadruples. (Water freezes at 273 K.) What is the value for α\alphaα , the temperature coefficient of resistivity?

A hair dryer draws 1500 W, a curling iron draws 800 W, and an electric light fixture draws 500 W. If all three of these appliances are operating in parallel on a 120 V circuit, what is the total current drawn?

Carbon has a negative temperature coefficient of resistance of -0.5 *10-3 (°C) - 1. What temperature increase would result in a resistance decrease of 3% for a carbon resistor?

What is the maximum number of 60-W light bulbs you can connect in parallel in a 120-V home circuit without tripping the 20-A circuit breaker?

A metal wire has a resistance of 25.00 Ω\OmegaΩ under room temperature conditions of 25°C. When the wire is heated to 85°C the resistance increases by 1.95 Ω\OmegaΩ . What is the temperature coefficient of resistivity of this metal?

A metal wire has a resistance of 10.00 Ω\OmegaΩ at a temperature of 20.0°C. If the same wire has a resistance of 10.55 Ω\OmegaΩ at 90°C, what is the resistance when its temperature is 0.0°C?

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

A tungsten wire is used to determine the melting point of indium. The resistance of the tungsten wire is 6.000 Ω\OmegaΩ at 20°C and increases to 9.700 Ω\OmegaΩ as the indium starts to melt. α\alphaα tungsten = 4.50 * 10 - 3 (°C) - 1. What is the melting temperature of indium?

A 22- Ω\OmegaΩ platinum wire at 20°C with a temperature coefficient of resistivity of 3.9 *10 - 3 (°C) - 1 will have what resistance at 100°C?

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

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

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

A certain material is in a room at 27°C. If the absolute temperature (K) of the material is tripled, its resistance quadruples. (Water freezes at 273 K.) What is the value for $\alpha$ , the temperature coefficient of resistivity?

Carbon has a negative temperature coefficient of resistance of -0.5 *10^-3 (°C) ^- ¹. What temperature increase would result in a resistance decrease of 3% for a carbon resistor?

A metal wire has a resistance of 25.00 $\Omega$ under room temperature conditions of 25°C. When the wire is heated to 85°C the resistance increases by 1.95 $\Omega$ . What is the temperature coefficient of resistivity of this metal?

A metal wire has a resistance of 10.00 $\Omega$ at a temperature of 20.0°C. If the same wire has a resistance of 10.55 $\Omega$ at 90°C, what is the resistance when its temperature is 0.0°C?

A tungsten wire is used to determine the melting point of indium. The resistance of the tungsten wire is 6.000 $\Omega$ at 20°C and increases to 9.700 $\Omega$ as the indium starts to melt. $\alpha$ _tungsten = 4.50 * 10 ^- ³ (°C) ^- ¹. What is the melting temperature of indium?

A 22- $\Omega$ platinum wire at 20°C with a temperature coefficient of resistivity of 3.9 *10 ^- ³ (°C) ^- ¹ will have what resistance at 100°C?