Question 1

A 100-W light bulb is in a socket supplied with 120 V. What is the current in the bulb?

Accepted Answer

Using Ohm's law, we have:
V = IR
where V is the voltage (120 V), I is the current we want to find, and R is the resistance of the bulb. We know that the power P of the bulb is 100 W, and that power is also given by:
P = IV
where V is the voltage across the bulb and I is the current through the bulb. Rearranging this equation to solve for I, we get:
I = P/V
Substituting the given values, we get:
I = 100/120 = 0.83 A
Therefore, the correct answer is B.

Question 2

The unit for rate of energy transformation, the watt, in an electric circuit is equivalent to which of the following?

Accepted Answer

The watt is equivalent to one joule per second, which can be expressed as volts times amperes (V·A) in an electric circuit.

Question 3

A high-voltage transmission line carries 500 A at 700,000 V. What is the power carried by the line?

Accepted Answer

Power = Voltage x Current
Power = 700,000 V x 500 A
Power = 350,000,000 W
Power = 350 MW

Question 4

A copper cable needs to carry a current of 200 A with a power loss of only 1.5 W/m. What is the required radius of the copper cable? (The resistivity of copper is 1.7 *10 ^- ⁸ $\Omega$m.)

Accepted Answer

The answer of A copper cable needs to carry a...

Question 5

A length L of wire has a voltage V across its ends while a current I runs through the wire. If a voltage 3V were applied to another length of this same wire from the same coil and the same current were found to run through it, what is the length of this second wire?

Accepted Answer

The answer of A length L of wire has a...

Question 6

If a 9.0-V battery, with negligible internal resistance, and an 27-$\Omega$ resistor are connected in series, what is the amount of electrical energy transformed to heat per coulomb of charge that flows through the circuit?

Accepted Answer

The answer of If a 9.0-V battery, with negligible internal...

Question 7

A high-voltage transmission line carries 500 A at 700 kV for a distance of 100 miles. If the resistance in the wire is 1 $\Omega$/mile, what is the power loss due to resistive losses?

Accepted Answer

The power loss due to resistive losses (P_loss) is calculated using the formula P_loss = I^2 * R, where I is the current and R is the total resistance. The resistance per mile is 1 ohm/mile, so for 100 miles, the total resistance is 100 ohms. Thus, P_loss = (500 A)^2 * 100 ohms = 25,000,000 W or 25 MW.

Question 8

An electric clothes dryer draws 20 A at 220 V. If the clothes put into the dryer have a mass of 7.0 kg when wet and 3.0 kg dry, 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 power of the dryer is P = IV = 20 A * 220 V = 4400 W. The energy required to vaporize the water is Q = mL = (7.0 kg - 3.0 kg) * 2.26 * 10^6 J/kg = 9.04 * 10^6 J. The time required is t = Q/P = 9.04 * 10^6 J / 4400 W = 2054.55 s, which is approximately 34 minutes.

Question 9

If a lamp has resistance of 120 $\Omega$when it operates at 200 W, what is the applied voltage?

Accepted Answer

The answer of If a lamp has resistance of 120...

Question 10

A resistor is connected to a battery with negligible internal resistance. If you replace the resistor with one that has quadruple the resistance, by what factor does the power dissipated in the circuit change?

Accepted Answer

The answer of A resistor is connected to a battery...

Question 11

The quantity volt is equivalent to which of the following?

Accepted Answer

A volt is defined as one joule per coulomb (J/C), which is the unit of electric potential difference.

Question 12

An electric car is designed to run off a bank of 12-V batteries with total energy storage of 6.0 *10⁷ J. If the electric motor draws 6000 W in moving the car at a steady speed of 10 m/s, how far will the car go before it is "out of juice?"

Accepted Answer

The total energy storage is 6.0 x 10^7 J. The power drawn by the motor is 6000 W, which means it uses 6000 J/s. The time it can run is 6.0 x 10^7 J / 6000 J/s = 10,000 s. At a speed of 10 m/s, the distance covered is 10 m/s * 10,000 s = 100,000 m, or 100 km.

Question 13

A light bulb, sold as long-lasting, is rated 120 W at 130 V. The "increased" lifetime comes from using it at 120 V. Assuming negligible change in resistance at the different voltage, what is its power consumption at 120 V?

Accepted Answer

The answer of A light bulb, sold as long-lasting, is...

Question 14

Ten coulombs of charge start from the negative terminal of a battery, flow through the battery and then leave the positive terminal through a wire, flow through a resistor, and then return to the starting point on this closed circuit. In this complete process, the ten coulombs:

Accepted Answer

In a closed circuit, the charge returns to its starting point, meaning there is no net change in potential energy.

Question 15

A wire of length L is uniformly stretched to triple its original length.By what factor does its resistance change?

Accepted Answer

The answer of A wire of length L is uniformly...

Question 16

A water pump draws about 4.4 A when connected to 240 V. What is the cost (with electrical energy at 9 cents per kWh) of running the pump for 10 h?

Accepted Answer

We can use the formula:

Energy = power x time = current x voltage x time

First, we need to convert the current to power:

Power = current x voltage = 4.4 A x 240 V = 1056 W

Now we can calculate the energy used:

Energy = power x time = 1056 W x 10 h = 10560 Wh = 10.56 kWh

Finally, we can calculate the cost:

Cost = energy x cost per kWh = 10.56 kWh x $0.09/kWh = $0.95

Therefore, the cost of running the pump for 10 hours is $0.95, which corresponds to choice C.

Question 17

If a light bulb has half the resistance of a 50-W lightbulb, what would be its wattage? Assume both bulbs are attached to the same 120-V circuit.

Accepted Answer

We can use Ohm's Law and the formula for power (P=V^2/R) to solve for the wattage of the new light bulb.

Let R be the resistance of the 50 W bulb, then:

P = V^2/R
50 = 120^2/R
R = 28.8 ohms

Let R' be the resistance of the new light bulb, then:

R' = R/2 = 14.4 ohms

And:

P' = V^2/R' = 120^2/14.4 = 100 W

Therefore, the wattage of the new light bulb would be 100 W. Answer: D.

Question 18

Three wires of the same diameter and length are made from three different metals: copper (  ), aluminum (  ), and silver (  ). Which wire has the least resistance?

Accepted Answer

The answer of Three wires of the same diameter and...

Question 19

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

Accepted Answer

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

Question 20

If a 500-W heater carries a current of 2.00 A, what is the voltage across the ends of the heating element?

Accepted Answer

Using Ohm's Law, we can find the voltage:
V = I*R
where I is the current and R is the resistance of the heating element.
Also, we know that power = voltage * current, so we can write:
P = V*I
Rearranging this equation, we get:
V = P/I
Plugging in the given values, we get:
V = 500 W / 2.00 A = 250 V

Quiz 19: Electric Currents and Circuits

A 100-W light bulb is in a socket supplied with 120 V. What is the current in the bulb?

The unit for rate of energy transformation, the watt, in an electric circuit is equivalent to which of the following?

A high-voltage transmission line carries 500 A at 700,000 V. What is the power carried by the line?

A copper cable needs to carry a current of 200 A with a power loss of only 1.5 W/m. What is the required radius of the copper cable? (The resistivity of copper is 1.7 *10 ^- ⁸ $\Omega$ m.)

A length L of wire has a voltage V across its ends while a current I runs through the wire. If a voltage 3V were applied to another length of this same wire from the same coil and the same current were found to run through it, what is the length of this second wire?

If a 9.0-V battery, with negligible internal resistance, and an 27- $\Omega$ resistor are connected in series, what is the amount of electrical energy transformed to heat per coulomb of charge that flows through the circuit?

A high-voltage transmission line carries 500 A at 700 kV for a distance of 100 miles. If the resistance in the wire is 1 $\Omega$ /mile, what is the power loss due to resistive losses?

An electric clothes dryer draws 20 A at 220 V. If the clothes put into the dryer have a mass of 7.0 kg when wet and 3.0 kg dry, how long does it take to dry the clothes? (Assume all heat energy goes into vaporizing water, L_v = 2.26 *10⁶ J/kg.)

If a lamp has resistance of 120 $\Omega$ when it operates at 200 W, what is the applied voltage?

A resistor is connected to a battery with negligible internal resistance. If you replace the resistor with one that has quadruple the resistance, by what factor does the power dissipated in the circuit change?

The quantity volt is equivalent to which of the following?

An electric car is designed to run off a bank of 12-V batteries with total energy storage of 6.0 *10⁷ J. If the electric motor draws 6000 W in moving the car at a steady speed of 10 m/s, how far will the car go before it is "out of juice?"

A light bulb, sold as long-lasting, is rated 120 W at 130 V. The "increased" lifetime comes from using it at 120 V. Assuming negligible change in resistance at the different voltage, what is its power consumption at 120 V?

Ten coulombs of charge start from the negative terminal of a battery, flow through the battery and then leave the positive terminal through a wire, flow through a resistor, and then return to the starting point on this closed circuit. In this complete process, the ten coulombs:

A wire of length L is uniformly stretched to triple its original length.By what factor does its resistance change?

A water pump draws about 4.4 A when connected to 240 V. What is the cost (with electrical energy at 9 cents per kWh) of running the pump for 10 h?

If a light bulb has half the resistance of a 50-W lightbulb, what would be its wattage? Assume both bulbs are attached to the same 120-V circuit.

Three wires of the same diameter and length are made from three different metals: copper ( ) , aluminum ( ) , and silver ( ) . Which wire has the least resistance?

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

If a 500-W heater carries a current of 2.00 A, what is the voltage across the ends of the heating element?

Quiz 19: Electric Currents and Circuits

A 100-W light bulb is in a socket supplied with 120 V. What is the current in the bulb?

The unit for rate of energy transformation, the watt, in an electric circuit is equivalent to which of the following?

A high-voltage transmission line carries 500 A at 700,000 V. What is the power carried by the line?

A copper cable needs to carry a current of 200 A with a power loss of only 1.5 W/m. What is the required radius of the copper cable? (The resistivity of copper is 1.7 *10 - 8 Ω\OmegaΩ m.)

A length L of wire has a voltage V across its ends while a current I runs through the wire. If a voltage 3V were applied to another length of this same wire from the same coil and the same current were found to run through it, what is the length of this second wire?

If a 9.0-V battery, with negligible internal resistance, and an 27- Ω\OmegaΩ resistor are connected in series, what is the amount of electrical energy transformed to heat per coulomb of charge that flows through the circuit?

A high-voltage transmission line carries 500 A at 700 kV for a distance of 100 miles. If the resistance in the wire is 1 Ω\OmegaΩ /mile, what is the power loss due to resistive losses?

An electric clothes dryer draws 20 A at 220 V. If the clothes put into the dryer have a mass of 7.0 kg when wet and 3.0 kg dry, how long does it take to dry the clothes? (Assume all heat energy goes into vaporizing water, Lv = 2.26 *106 J/kg.)

If a lamp has resistance of 120 Ω\OmegaΩ when it operates at 200 W, what is the applied voltage?

A resistor is connected to a battery with negligible internal resistance. If you replace the resistor with one that has quadruple the resistance, by what factor does the power dissipated in the circuit change?

The quantity volt is equivalent to which of the following?

An electric car is designed to run off a bank of 12-V batteries with total energy storage of 6.0 *107 J. If the electric motor draws 6000 W in moving the car at a steady speed of 10 m/s, how far will the car go before it is "out of juice?"

A light bulb, sold as long-lasting, is rated 120 W at 130 V. The "increased" lifetime comes from using it at 120 V. Assuming negligible change in resistance at the different voltage, what is its power consumption at 120 V?

Ten coulombs of charge start from the negative terminal of a battery, flow through the battery and then leave the positive terminal through a wire, flow through a resistor, and then return to the starting point on this closed circuit. In this complete process, the ten coulombs:

A wire of length L is uniformly stretched to triple its original length.By what factor does its resistance change?

A water pump draws about 4.4 A when connected to 240 V. What is the cost (with electrical energy at 9 cents per kWh) of running the pump for 10 h?

If a light bulb has half the resistance of a 50-W lightbulb, what would be its wattage? Assume both bulbs are attached to the same 120-V circuit.

Three wires of the same diameter and length are made from three different metals: copper ( ) , aluminum ( ) , and silver ( ) . Which wire has the least resistance?

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

If a 500-W heater carries a current of 2.00 A, what is the voltage across the ends of the heating element?

A copper cable needs to carry a current of 200 A with a power loss of only 1.5 W/m. What is the required radius of the copper cable? (The resistivity of copper is 1.7 *10 ^- ⁸ $\Omega$ m.)

If a 9.0-V battery, with negligible internal resistance, and an 27- $\Omega$ resistor are connected in series, what is the amount of electrical energy transformed to heat per coulomb of charge that flows through the circuit?

A high-voltage transmission line carries 500 A at 700 kV for a distance of 100 miles. If the resistance in the wire is 1 $\Omega$ /mile, what is the power loss due to resistive losses?

An electric clothes dryer draws 20 A at 220 V. If the clothes put into the dryer have a mass of 7.0 kg when wet and 3.0 kg dry, how long does it take to dry the clothes? (Assume all heat energy goes into vaporizing water, L_v = 2.26 *10⁶ J/kg.)

If a lamp has resistance of 120 $\Omega$ when it operates at 200 W, what is the applied voltage?

An electric car is designed to run off a bank of 12-V batteries with total energy storage of 6.0 *10⁷ J. If the electric motor draws 6000 W in moving the car at a steady speed of 10 m/s, how far will the car go before it is "out of juice?"