Question 1

If a lamp has resistance of 120 W when it operates at 100 W, what is the applied voltage?
A)110 V
B)120 V
C)125 V
D)220 V

Accepted Answer

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

Question 2

A light bulb has resistance of 240 W when operating at 120 V.Find the current in the light bulb.
A)2.0 A
B)1.0 A
C)0.50 A
D)0.20 A

Accepted Answer

Using Ohm's Law, we can find the current (I) in the light bulb: 
R = V/I 
240 Ω = 120 V / I 
I = 0.5 A

Question 3

Which process will double the power given off by a resistor?
A)doubling the current while doubling the resistance
B)doubling the current by making a resistance half as big
C)doubling the current by doubling the voltage
D)doubling the current while making the voltage half as big

Accepted Answer

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

Question 4

The heating coil of a hot water heater has a resistance of 20 W and operates at 210 V.How long a time is required to raise the temperature of 200 kg of water from 15$\degree$C to 80$\degree$C? (The specific heat for water = 10³ cal/kg*$\degree$C and 1.0 cal = 4.186 J). A)1.7 h B)3.8 h C)5.1 h D)6.9 h

Accepted Answer

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

Question 5

If a lamp has a resistance of 120 W when it operates at 100 W, what current does it carry?
A)2.10 A
B)1.2 A
C)0.91 A
D)0.83 A

Accepted Answer

We can use Ohm's Law to solve for current:

I = P / V

where P is the power in watts and V is the voltage in volts. Since the voltage is not given, we can use the given resistance to solve for it:

R = V / I

rearranging:

V = R * I

Now we can substitute this expression for V into Ohm's Law:

I = P / (R * I)

multiplying both sides by I:

I^2 = P / R

taking the square root:

I = sqrt(P / R)

Plugging in the given values, we get:

I = sqrt(100 / 120) = 0.91 A

So the answer is C, 0.91 A.

Question 6

A high-voltage transmission line carries 1 000 A at 700 000 V.What is the power carried by the line?
A)700 MW
B)370 MW
C)100 MW
D)70 MW

Accepted Answer

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

Question 7

The quantity volt is equivalent to which of the following?
A)J*m
B)J*C
C)C/W
D)J/C

Accepted Answer

The unit volt is defined as the potential difference across a conductor when a current of one ampere dissipates one watt of power. In other words, 1 volt = 1 joule/coulomb or 1 J/C. Therefore, the option D - J/C is the correct answer.

Question 8

An electric clothes dryer draws 15 A at 220 V.If the clothes put into the dryer have a mass of 7.0 kg when wet and 4.0 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). A)55 min B)34 min C)20 min D)16 min

Accepted Answer

First, we need to find the amount of energy needed to vaporize the water: Energy = L_v * (mass of wet clothes - mass of dry clothes) = 2.26 * 10⁶ * (7.0 kg - 4.0 kg) = 6.78 * 10⁶ J The time required to generate this energy can be found using the formula: Energy = Power x time, so time = Energy / Power Substituting the values, we get: time = 6.78 * 10⁶ J / (15 A x 220 V) = 34.2 min ≈ 34 min Therefore, the correct answer is B.

Question 9

If a 500-W heater carries a current of 4.00 A, what is the resistance of the heating element?
A)85.7 W
B)42.8 W
C)31.3 W
D)11.2 W

Accepted Answer

Using the formula P = I^2 * R, we can rearrange it to get R = P / I^2. Substituting the given values, we get R = 500 W / (4.00 A)^2 = 31.3 Ω. Therefore, the answer is C.

Question 10

Which is not a force?
A)gravity
B)electrical force
C)voltage
D)friction

Accepted Answer

Voltage is a measure of electric potential difference, it is not a force. The other options listed (gravity, electrical force, and friction) are all forces.

Question 11

An electric toaster requires 1 100 W at 110 V.What is the resistance of the heating coil?
A)7.5 W
B)9.0 W
C)10.0 W
D)11.0 W

Accepted Answer

The answer of An electric toaster requires 1 100 W...

Question 12

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)do positive work on the battery.
B)receive heat energy from the resistor.
C)have a net loss of potential energy.
D)have no net change in potential energy.

Accepted Answer

According to the law of conservation of energy, the net change in potential energy of a closed circuit must be zero. Therefore, the ten coulombs of charge have no net change in potential energy as they return to the starting point. Additionally, the charge does not do positive work on the battery and does not receive heat energy from the resistor, as those processes would involve a net change in energy.

Question 13

If a 500-W heater carries a current of 4.00 A, what is the voltage across the ends of the heating element?
A)2 000 V
B)125 V
C)250 V
D)0.008 V

Accepted Answer

The answer of If a 500-W heater carries a current...

Question 14

A light bulb, sold as long-lasting, is rated 100 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?
A)85 W
B)92 W
C)100 W
D)108 W

Accepted Answer

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

Question 15

The unit for rate of energy transformation, the watt, in an electric circuit is equivalent to which of the following?
A)V/s
B)A*W
C)V*A
D)V/W

Accepted Answer

The answer of The unit for rate of energy transformation,...

Question 16

A resistor is connected to a battery with negligible internal resistance.If you replace the resistor with one that has twice the resistance, by what factor does the power dissipated in the circuit change?
A)0.50
B)0.25
C)4.0
D)2.0

Accepted Answer

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

Question 17

If electrical energy costs 5.5 cents per kWh, what does it cost to heat 200 kg water from 15$\degree$C to 80$\degree$C? (The specific heat of water = 10³ cal/kg*$\degree$C and 1.0 cal = 4.186 J.) A)48 cents B)83 cents C)16 cents D)80 cents

Accepted Answer

First, we need to calculate the amount of energy required to heat the water:

Q = mCΔT

Where:
m = mass of water = 200 kg
C = specific heat of water = 10.13 cal/kg∙°C
ΔT = change in temperature = 80°C - 15°C = 65°C

Q = (200 kg) (10.13 cal/kg∙°C) (65°C) = 131,845 cal

Since 1.0 cal = 4.186 J, we can convert the energy in calories to joules:

Q = (131,845 cal)(4.186 J/cal) = 552,656 J

To convert joules to kWh, we divide by 3,600,000 (the number of joules in one kilowatt-hour):

Q = (552,656 J)/(3,600,000 J/kWh) = 0.1535 kWh

Finally, we can calculate the cost of this energy:

Cost = (0.1535 kWh)($0.055/kWh) = $0.0084

Therefore, the cost to heat the water is 8.4 cents, which is closest to option B (83 cents).

Question 18

A steam turbine at an electric power plant delivers 4 500 kW of power to an electrical generator which converts 95% of this mechanical energy into electrical energy.What is the current delivered by the generator if it delivers at 3 600 V? A)0.66 * 10³ A B)1.0 * 10³ A C)1.2 * 10³ A D)5.9 * 10³ A

Accepted Answer

The electrical power output can be found using the equation:
Power = Current x Voltage
We know that the power delivered by the turbine is 4,500 kW and that the electrical energy output is 95% of this, so:
Electrical power output = 4,500 kW x 0.95 = 4,275 kW
Now we can rearrange the power equation to solve for current:
Current = Power / Voltage
Current = 4,275 kW / 3,600 V = 1.1875 * 103 A
Rounding to 2 significant figures gives the answer of 1.2 * 103 A, which corresponds to choice C.

Question 19

A water pump draws about 3.8 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?
A)8.0 cents
B)15 cents
C)82 cents
D)95 cents

Accepted Answer

First, we need to calculate the power consumed by the water pump:

Power (P) = Voltage (V) x Current (I)
P = 240 V x 3.8 A
P = 912 watts = 0.912 kW

Next, we can calculate the energy consumed by the water pump over the 10 hour period:

Energy (E) = Power (P) x Time (t)
E = 0.912 kW x 10 h
E = 9.12 kWh

Finally, we can calculate the cost of this energy based on the given rate of 9 cents per kWh:

Cost = Energy x Rate
Cost = 9.12 kWh x $0.09/kWh
Cost = $0.82 or 82 cents

Therefore, the best choice is C, 82 cents.

Question 20

Which is a unit of power?
A)kWh
B)W/s
C)A*W
D)J/s

Accepted Answer

J/s is the unit of power, also known as Watt (W). kWh is a unit of energy, W/s is not a recognized unit, and AF1F1F1S1F1F1F10W is not a valid unit.

Quiz 17: Current and Resistance

If a lamp has resistance of 120 W when it operates at 100 W, what is the applied voltage?

A light bulb has resistance of 240 W when operating at 120 V.Find the current in the light bulb.

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

The heating coil of a hot water heater has a resistance of 20 W and operates at 210 V.How long a time is required to raise the temperature of 200 kg of water from 15 $\degree$ C to 80 $\degree$ C? (The specific heat for water = 10³ cal/kg* $\degree$ C and 1.0 cal = 4.186 J) .

If a lamp has a resistance of 120 W when it operates at 100 W, what current does it carry?

A high-voltage transmission line carries 1 000 A at 700 000 V.What is the power carried by the line?

The quantity volt is equivalent to which of the following?

An electric clothes dryer draws 15 A at 220 V.If the clothes put into the dryer have a mass of 7.0 kg when wet and 4.0 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 500-W heater carries a current of 4.00 A, what is the resistance of the heating element?

Which is not a force?

An electric toaster requires 1 100 W at 110 V.What is the resistance of the heating coil?

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:

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

A light bulb, sold as long-lasting, is rated 100 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?

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

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

If electrical energy costs 5.5 cents per kWh, what does it cost to heat 200 kg water from 15 $\degree$ C to 80 $\degree$ C? (The specific heat of water = 10³ cal/kg* $\degree$ C and 1.0 cal = 4.186 J.)

A steam turbine at an electric power plant delivers 4 500 kW of power to an electrical generator which converts 95% of this mechanical energy into electrical energy.What is the current delivered by the generator if it delivers at 3 600 V?

A water pump draws about 3.8 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?

Which is a unit of power?