Question 1

If a lamp has resistance of 140 Ω when it operates at 130 W,what is the applied voltage?

Accepted Answer

The applied voltage can be calculated using the formula V = √(P * R), where P is power and R is resistance. Substituting the given values, V = √(130 W * 140 Ω) = √18200 = 135 V.

Question 2

An electric car is designed to run off a bank of 14.0-V batteries with total energy storage of 3.00 × 10⁷ J.If the electric motor draws 7 000 W,what current will be delivered to the motor?

Accepted Answer

The current can be calculated using the formula P = IV, where P is power, I is current, and V is voltage. Rearranging gives I = P/V. Substituting the given values, I = 7000 W / 14.0 V = 500 A.

Question 3

Which is a unit of power?

Accepted Answer

J/s, also known as watts, is the unit of power. kWh is a unit of energy, W/s is not a recognized unit, and A⋅Ω is a unit of electrical resistance.

Question 4

An electric car is designed to run off a bank of 15-V batteries with total energy storage of 2.1 × 10⁷ J.If the electric motor draws 4 200 W in moving the car at a steady speed of 14 m/s,how far will the car go before it is "out of juice?"

Accepted Answer

The total energy available is 2.1 × 10^7 J. The power drawn by the motor is 4,200 W, which means it uses 4,200 J/s. The time the car can run is 2.1 × 10^7 J / 4,200 J/s = 5,000 s. At a speed of 14 m/s, the distance covered is 14 m/s * 5,000 s = 70,000 m, which is 70 km.

Question 5

A light bulb has resistance of 175 Ω when operating at 100 V.Find the current in the light bulb.

Accepted Answer

Using Ohm's Law, we have:
I = V/R
I = 100/175
I = 0.57 A

Question 6

A high-voltage transmission line carries 1 400 A at 600 000 V.What is the power carried by the line?

Accepted Answer

The power carried by the line can be calculated using the formula P = IV, where P is power in watts, I is current in amperes, and V is voltage in volts. Substituting the given values, P = 1400 A * 600,000 V = 840,000,000 W or 840 MW.

Question 7

An electric clothes dryer draws 10 A at 220 V.If the clothes put into the dryer have a mass of 10 kg when wet and 3 kg dry,about how long does it take to dry the clothes? (Assume all heat energy goes into vaporizing water,L_v = 2.26 × 10⁶ J/kg).

Accepted Answer

The answer of An electric clothes dryer draws 10 A...

Question 8

Which is not a force?

Accepted Answer

Voltage is a measure of electric potential difference, which is not a force itself but can create an electrical force if there is a charge imbalance. Gravity, electrical force, and friction are all considered forces.

Question 9

A steam turbine at an electric power plant delivers 4 500 kW of power to an electrical generator which converts 94% of this mechanical energy into electrical energy.What is the current delivered by the generator if it delivers at 3 500 V?

Accepted Answer

The electrical power delivered by the generator is given by the formula P = IV, where P is power, I is current, and V is voltage. We can rearrange this formula to get I = P/V. First, we need to find the electrical power output of the generator, which is:
P = 0.94 x 4 500 kW = 4 230 kW
Then we can plug in the values for P and V to find I:
I = 4 230 kW / 3 500 V = 1 209 A
Therefore, the current delivered by the generator is 1.2E+3 A, which is closest to choice C, 1.2E+3 A.

Question 10

A 500-W heater carries a current of 4.0 A.How much does it cost to operate the heater for 30 min if electrical energy costs 6.0 cents per kWh?

Accepted Answer

The power of the heater is given as 500 W (or 0.5 kW), and it operates for 30 minutes (or 0.5 hours). The cost of electrical energy is 6.0 cents per kWh. To find the cost of operating the heater, multiply the power by the time and then by the cost per kWh: $0.5 \text{ kW} \times 0.5 \text{ hours} \times 6.0 \text{ cents/kWh} = 1.5 \text{ cents}$.

Question 11

A water pump draws about 3.7 A when connected to 220 V.What is the cost (with electrical energy at 6.0 cents per kWh)of running the pump for 7.0 h?

Accepted Answer

Power (P) = VI
= 220 V × 3.7 A
= 814 W

Energy consumed (E) = Pt
= 814 W × 7.0 h
= 5698 Wh
= 5.698 kWh

Cost of energy = Energy consumed × Cost per kWh
= 5.698 kWh × 6.0 cents/kWh
= 34.188 cents
≈ 34 cents

Therefore, the cost of running the pump for 7.0 hours is approximately 34 cents.

Question 12

A light bulb,sold as long-lasting,is rated 95 W at 145 V.The "increased" lifetime comes from using it at 110 V.Assuming negligible change in resistance at the different voltage,what is its power consumption at 110 V?

Accepted Answer

The power consumption at a lower voltage can be calculated using the formula $P = \frac{V^2}{R}$, where $P$ is power, $V$ is voltage, and $R$ is resistance. Since resistance ($R$) remains constant, we can set up a ratio of the power consumptions at the two voltages: $\frac{P_1}{P_2} = \frac{V_1^2}{V_2^2}$. Given $P_1 = 95W$ and $V_1 = 145V$, and $V_2 = 110V$, solving for $P_2$ gives $P_2 = 95W \times (\frac{110V}{145V})^2 \approx 55W$.

Question 13

If a 500-W heater carries a current of 4.00 A,what is the resistance of the heating element?

Accepted Answer

The resistance can be calculated using the formula $P = I^2R$, where $P$ is the power (500 W), $I$ is the current (4.00 A), and $R$ is the resistance. Rearranging the formula to solve for $R$ gives $R = P / I^2$. Substituting the given values, $R = 500 / (4.00)^2 = 500 / 16 = 31.25 \Omega$, which rounds to 31.3 Ω.

Question 14

If a lamp has a resistance of 265 Ω when it operates at 250 W,what current does it carry?

Accepted Answer

To find the current, use the formula P = I^2 * R, where P is power, I is current, and R is resistance. Rearranging gives I = sqrt(P/R). Substituting the given values, I = sqrt(250/265) ≈ 0.97 A.

Question 15

A solar panel measures 80 cm × 57 cm.In direct sunlight,the panel delivers 3.1 A at 15 V.If the intensity of sunlight is 1 000 W/m²,what is the efficiency of the solar panel in converting solar energy into electrical energy?

Accepted Answer

Firstly, we need to calculate the area of the solar panel by multiplying its length and breadth in meters:
Area = (80 cm × 57 cm) ÷ (100 cm/m)² = 0.456 m²

Next, we can calculate the power output of the solar panel in direct sunlight:
Power = Current × Voltage = 3.1 A × 15 V = 46.5 W

We can now determine the intensity of sunlight on the solar panel:
Sunlight intensity = Power ÷ Area = 46.5 W ÷ 0.456 m² = 102 W/m²

Finally, we can calculate the efficiency of the solar panel:
Efficiency = (Power output ÷ Solar energy input) × 100%
Efficiency = (46.5 W ÷ 1020 W) × 100% = 4.56%

Therefore, the best choice is C with an efficiency of 10%.

Question 16

A high-voltage transmission line carries 1 000 A at 700 kV for a distance of 200 miles.If the resistance in the wire is 1 Ω/mile,what is the power loss due to resistive losses?

Accepted Answer

The answer of A high-voltage transmission line carries 1 000...

Question 17

The heating coil of a hot water heater has a resistance of 17 Ω and operates at 300 V.How long a time is required to raise the temperature of 115 kg of water from 18°C to 75°C? (The specific heat for water = 10³ cal/kg⋅°C and 1.0 cal = 4.186 J).

Accepted Answer

The answer of The heating coil of a hot water...

Question 18

Suppose that a voltage surge produces 140 V for a moment in a 115-V line.What will temporarily be the output of a 100-W light bulb assuming its resistance does not change?

Accepted Answer

First, we need to calculate the normal resistance (R) of the 100-W light bulb using the formula:

P = V^2 / R

where P is the power (100 W), V is the voltage (115 V), and R is the resistance.

R = V^2 / P = 115^2 / 100 = 132.25 ohms

When a voltage surge produces 140 V, the current (I) through the bulb will increase, since I = V / R.

I = 140 / 132.25 = 1.06 A

Using this current value and the original resistance of the bulb, we can calculate the temporary power (P') using the formula:

P' = I^2 * R = 1.06^2 * 132.25 = 148 W

Therefore, the answer is D) 148 W.

Question 19

An electric toaster requires 1 300 W at 150 V.What is the resistance of the heating coil?

Accepted Answer

The answer of An electric toaster requires 1 300 W...

Question 20

Which process will double the power given off by a resistor?

Accepted Answer

The answer of Which process will double the power given...

Quiz 17: Current and Resistance

If a lamp has resistance of 140 Ω when it operates at 130 W,what is the applied voltage?

An electric car is designed to run off a bank of 14.0-V batteries with total energy storage of 3.00 × 10⁷ J.If the electric motor draws 7 000 W,what current will be delivered to the motor?

Which is a unit of power?

An electric car is designed to run off a bank of 15-V batteries with total energy storage of 2.1 × 10⁷ J.If the electric motor draws 4 200 W in moving the car at a steady speed of 14 m/s,how far will the car go before it is "out of juice?"

A light bulb has resistance of 175 Ω when operating at 100 V.Find the current in the light bulb.

A high-voltage transmission line carries 1 400 A at 600 000 V.What is the power carried by the line?

An electric clothes dryer draws 10 A at 220 V.If the clothes put into the dryer have a mass of 10 kg when wet and 3 kg dry,about how long does it take to dry the clothes? (Assume all heat energy goes into vaporizing water,L_v = 2.26 × 10⁶ J/kg) .

Which is not a force?

A steam turbine at an electric power plant delivers 4 500 kW of power to an electrical generator which converts 94% of this mechanical energy into electrical energy.What is the current delivered by the generator if it delivers at 3 500 V?

A 500-W heater carries a current of 4.0 A.How much does it cost to operate the heater for 30 min if electrical energy costs 6.0 cents per kWh?

A water pump draws about 3.7 A when connected to 220 V.What is the cost (with electrical energy at 6.0 cents per kWh) of running the pump for 7.0 h?

A light bulb,sold as long-lasting,is rated 95 W at 145 V.The "increased" lifetime comes from using it at 110 V.Assuming negligible change in resistance at the different voltage,what is its power consumption at 110 V?

If a 500-W heater carries a current of 4.00 A,what is the resistance of the heating element?

If a lamp has a resistance of 265 Ω when it operates at 250 W,what current does it carry?

A solar panel measures 80 cm × 57 cm.In direct sunlight,the panel delivers 3.1 A at 15 V.If the intensity of sunlight is 1 000 W/m²,what is the efficiency of the solar panel in converting solar energy into electrical energy?

A high-voltage transmission line carries 1 000 A at 700 kV for a distance of 200 miles.If the resistance in the wire is 1 Ω/mile,what is the power loss due to resistive losses?

The heating coil of a hot water heater has a resistance of 17 Ω and operates at 300 V.How long a time is required to raise the temperature of 115 kg of water from 18°C to 75°C? (The specific heat for water = 10³ cal/kg⋅°C and 1.0 cal = 4.186 J) .

Suppose that a voltage surge produces 140 V for a moment in a 115-V line.What will temporarily be the output of a 100-W light bulb assuming its resistance does not change?

An electric toaster requires 1 300 W at 150 V.What is the resistance of the heating coil?

Which process will double the power given off by a resistor?

Quiz 17: Current and Resistance

If a lamp has resistance of 140 Ω when it operates at 130 W,what is the applied voltage?

An electric car is designed to run off a bank of 14.0-V batteries with total energy storage of 3.00 × 107 J.If the electric motor draws 7 000 W,what current will be delivered to the motor?

Which is a unit of power?

An electric car is designed to run off a bank of 15-V batteries with total energy storage of 2.1 × 107 J.If the electric motor draws 4 200 W in moving the car at a steady speed of 14 m/s,how far will the car go before it is "out of juice?"

A light bulb has resistance of 175 Ω when operating at 100 V.Find the current in the light bulb.

A high-voltage transmission line carries 1 400 A at 600 000 V.What is the power carried by the line?

An electric clothes dryer draws 10 A at 220 V.If the clothes put into the dryer have a mass of 10 kg when wet and 3 kg dry,about how long does it take to dry the clothes? (Assume all heat energy goes into vaporizing water,Lv = 2.26 × 106 J/kg) .

Which is not a force?

A steam turbine at an electric power plant delivers 4 500 kW of power to an electrical generator which converts 94% of this mechanical energy into electrical energy.What is the current delivered by the generator if it delivers at 3 500 V?

A 500-W heater carries a current of 4.0 A.How much does it cost to operate the heater for 30 min if electrical energy costs 6.0 cents per kWh?

A water pump draws about 3.7 A when connected to 220 V.What is the cost (with electrical energy at 6.0 cents per kWh) of running the pump for 7.0 h?

A light bulb,sold as long-lasting,is rated 95 W at 145 V.The "increased" lifetime comes from using it at 110 V.Assuming negligible change in resistance at the different voltage,what is its power consumption at 110 V?

If a 500-W heater carries a current of 4.00 A,what is the resistance of the heating element?

If a lamp has a resistance of 265 Ω when it operates at 250 W,what current does it carry?

A solar panel measures 80 cm × 57 cm.In direct sunlight,the panel delivers 3.1 A at 15 V.If the intensity of sunlight is 1 000 W/m2,what is the efficiency of the solar panel in converting solar energy into electrical energy?

A high-voltage transmission line carries 1 000 A at 700 kV for a distance of 200 miles.If the resistance in the wire is 1 Ω/mile,what is the power loss due to resistive losses?

The heating coil of a hot water heater has a resistance of 17 Ω and operates at 300 V.How long a time is required to raise the temperature of 115 kg of water from 18°C to 75°C? (The specific heat for water = 103 cal/kg⋅°C and 1.0 cal = 4.186 J) .

Suppose that a voltage surge produces 140 V for a moment in a 115-V line.What will temporarily be the output of a 100-W light bulb assuming its resistance does not change?

An electric toaster requires 1 300 W at 150 V.What is the resistance of the heating coil?

Which process will double the power given off by a resistor?

An electric car is designed to run off a bank of 14.0-V batteries with total energy storage of 3.00 × 10⁷ J.If the electric motor draws 7 000 W,what current will be delivered to the motor?

An electric car is designed to run off a bank of 15-V batteries with total energy storage of 2.1 × 10⁷ J.If the electric motor draws 4 200 W in moving the car at a steady speed of 14 m/s,how far will the car go before it is "out of juice?"

An electric clothes dryer draws 10 A at 220 V.If the clothes put into the dryer have a mass of 10 kg when wet and 3 kg dry,about how long does it take to dry the clothes? (Assume all heat energy goes into vaporizing water,L_v = 2.26 × 10⁶ J/kg) .

A solar panel measures 80 cm × 57 cm.In direct sunlight,the panel delivers 3.1 A at 15 V.If the intensity of sunlight is 1 000 W/m²,what is the efficiency of the solar panel in converting solar energy into electrical energy?

The heating coil of a hot water heater has a resistance of 17 Ω and operates at 300 V.How long a time is required to raise the temperature of 115 kg of water from 18°C to 75°C? (The specific heat for water = 10³ cal/kg⋅°C and 1.0 cal = 4.186 J) .