Question 1

When two identical resistors are connected in series across a battery,the total power dissipated by them is 20 W.If these resistors are connected in parallel across the same battery,the total power dissipated is
A)5 W
B)10 W
C)20 W
D)40 W
E)80 W

Accepted Answer

The answer of When two identical resistors are connected in...

Question 2

Battery A has a relatively high internal resistance,whereas battery B has a low internal resistance.If both batteries provide the same current to some external circuitry,which of the following statements is likely to be true?
A)Battery A is warmer to the touch than battery B.
B)Battery B is warmer to the touch than battery A.
C)Battery A is cooler to the touch than battery B.
D)Both batteries are equally warm to the touch.
E)The emf of both batteries must be known to predict their warmth to the touch.

Accepted Answer

The answer of Battery A has a relatively high internal...

Question 3

When two identical resistors are connected in parallel,the equivalent resistance,compared with that of the same two resistors connected in series,is
A)exactly the same.
B)twice as great.
C)one-half as much.
D)four times as great.
E)one-fourth as much.

Accepted Answer

When two identical resistors are connected in parallel, the equivalent resistance is given by the formula:
1/Req = 1/R1 + 1/R2
Since R1 = R2, we can write this as:
1/Req = 1/R + 1/R
Simplifying this, we get:
1/Req = 2/R
Multiplying both sides by R, we get:
Req = R/2 
Therefore, the equivalent resistance is one-half as much as that of the same two resistors connected in series.

Question 4

When two resistors are connected in series,the equivalent resistance is R_s = 10 $\Omega$.When they are connected in parallel,the equivalent resistance is R_p = 2.4 $\Omega$.What are the values of the two resistances? A)4.0 $\Omega$ and 6.0 $\Omega$ B)5.0 $\Omega$ for both C)1.0 $\Omega$ and 1.4 $\Omega$ D)1.2 $\Omega$ for both E)2.5 $\Omega$ and 7.5 $\Omega$

Accepted Answer

When two resistors are connected in series, their resistances add up, so $R_{series} = R_1 + R_2 = 10 \Omega$. When connected in parallel, the reciprocal of the total resistance is the sum of the reciprocals of each resistance, so $\frac{1}{R_{parallel}} = \frac{1}{R_1} + \frac{1}{R_2} = \frac{1}{2.4 \Omega}$. Solving these equations simultaneously gives the resistances as 4.0 Ω and 6.0 Ω.

Question 5

Two resistors are connected in series across a potential difference.If the current carried by resistor A is I,what is the current carried by B?
A)I
B)2I
C)I/2
D)4I
E)I/4

Accepted Answer

The answer of Two resistors are connected in series across...

Question 6

In a parallel circuit,
A)the current is the same in every branch.
B)the potential drop is the sum of those in all branches.
C)the potential drop is the same for each element of the parallel circuit.
D)the heat generated is the same in all branches.
E)the resistance is the sum of the resistances of the branches.

Accepted Answer

In a parallel circuit, the potential difference (voltage) across each branch is the same, regardless of the resistance within each branch. This is because each branch is directly connected to the voltage source.

Question 7

The conservation of charge in an electric circuit is closely related to which of the following?
A)Ohm's law
B)Kirchhoff's junction rule
C)Kirchhoff's loop rule
D)Newton's laws
E)Ampère's law

Accepted Answer

Kirchhoff's junction rule is directly related to the conservation of charge in an electric circuit. It states that the total current entering a junction equals the total current leaving the junction, reflecting the principle of charge conservation.

Question 8

A resistor of 2 $\Omega$ and another of 3 $\Omega$ are connected in parallel,and this combination is joined in series with a 4-$\Omega$ resistor across a battery.If the current in the 2-$\Omega$ resistor is 2.0 A,the potential drop across the 3-$\Omega$resistor is
A)2.4 V
B)1.2 V
C)6.0 V
D)4.0 V
E)8.0 V

Accepted Answer

The answer of A resistor of 2 $\Omega$ and another...

Question 9

The conservation of energy in an electric circuit is closely related to which of the following?
A)Ohm's law
B)Kirchhoff's junction rule
C)Kirchhoff's loop rule
D)Newton's laws
E)Ampère's law

Accepted Answer

The answer of The conservation of energy in an electric...

Question 10

A 12-V car battery may supply 60 A for 2.5 s in order for the starter motor to start the engine.Calculate how much electrical energy has been used. A)1.8 $\times$ 10³ J B)2.2 $\times$ 10⁴ J C)7.2 $\times$ 10² J D)3.6 $\times$ 10³ J E)4.5 $\times$ 10³ J

Accepted Answer

The answer of A 12-V car battery may supply 60...

Question 11

You leave your 120-W light bulb on in your room by mistake while you are at school for 8.5 hours.If the price of electrical energy is $0.085 per kilowatt-hour,how much did it cost you?
A)$0.082
B)$0.075
C)$0.065
D)$0.087
E)$0.078

Accepted Answer

The answer of You leave your 120-W light bulb on...

Question 12

A galvanometer has an internal resistance of 200 $\Omega$ and requires a current of 5.0 mA for full-scale deflection.What resistance should be connected in parallel with this galvanometer to make an ammeter that reads 10 A at full-scale deflection? A)0.10 $\Omega$ B)4.0 $\times$ 10⁵ $\Omega$ C)400 $\Omega$ D)0.20 $\Omega$ E)2.0 $\Omega$

Accepted Answer

The correct answer is A because the resistance of the ammeter is given by the formula:Ra = (Ig / Ig - If) * Rgwhere:Ra is the resistance of the ammeterIg is the current at full-scale deflection of the ammeterIf is the current at full-scale deflection of the galvanometerRg is the internal resistance of the galvanometerSubstituting the given values into the formula, we get:Ra = (10 A / 10 A - 5.0 mA) * 200 ΩRa = 0.10 Ω

Question 13

Two resistors R₁ and R₂ are connected in parallel,and this combination is connected in series with a third resistor R₃.If R₁ = 5.0 $\Omega$,R₂ = 2.0 $\Omega$,and R₃ = 6.0 $\Omega$,what is the equivalent resistance of this combination? A)0.3l $\Omega$ B)3.2 $\Omega$ C)6.7 $\Omega$ D)7.4 $\Omega$ E)13 $\Omega$

Accepted Answer

The equivalent resistance of resistors in parallel is given by 1/Req = 1/R1 + 1/R2. For R1 = 5Ω and R2 = 2Ω, 1/Req = 1/5 + 1/2 = 7/10, so Req = 10/7 Ω. Adding the series resistor (R3 = 6Ω) gives the total equivalent resistance: 10/7 Ω + 6Ω = 42/7 + 60/7 = 102/7 Ω = 14.57 Ω, which is closest to option D, 7.4 Ω.

Question 14

If it takes you 5 minutes to dry your hair using a 1200-W hairdryer plugged into a 120-V power outlet,how many Coulombs of charge pass through your hair dryer?
A)120 C
B)300 C
C)60.0 C
D)1.00 C
E)5.00 C

Accepted Answer

The charge (Q) in Coulombs can be calculated using the formula Q = It, where I is the current in amperes and t is the time in seconds. First, find the current using the power formula P = IV, where P is power (1200 W) and V is voltage (120 V). So, I = P/V = 1200W / 120V = 10A. The time is 5 minutes, which is 300 seconds (5 * 60). Therefore, Q = It = 10A * 300s = 3000 C.

Question 15

Two resistors are connected in parallel across a potential difference.The resistance of resistor A is twice that of resistor B.If the current carried by resistor A is I,what is the current carried by B?
A)I
B)2I
C)I/2
D)4I
E)I/4

Accepted Answer

The answer of Two resistors are connected in parallel across...

Question 16

In your four years at college you dry your hair everyday for 5 minutes with a 1200-W hairdryer.If the average price of electrical energy was $0.085 per kilowatt-hour,how much did it cost you during this time? (Assume 1 year = 365 days.)
A)$4.10
B)$8.90
C)$12.4
D)$22.8
E)$15.6

Accepted Answer

First, calculate the total energy used over four years: 1200 W = 1.2 kW, and drying time is 5 minutes per day. In hours, this is 5/60 hours per day. Over four years (4 * 365 days = 1460 days), the total energy used is 1.2 kW * (5/60) hours/day * 1460 days = 146 kWh. The cost is then 146 kWh * $0.085/kWh = $12.41, which rounds to $12.4.

Question 17

Each of three identical electric heaters is rated at 1000 W when operated across 100-V lines.When the three are connected in series across a 120-V line,at what rate is electric energy converted to heat energy? (Neglect variation of resistance with temperature.)
A)0.48 kW
B)1.0 kW
C)1.2 kW
D)3.0 kW
E)3.6 kW

Accepted Answer

The answer of Each of three identical electric heaters is...

Question 18

You connect two identical resistors in series across supply lines maintained at a constant potential difference.When you later connect them in parallel across the same supply lines,the total current furnished by the supply lines,compared with the former current,is
A)exactly the same.
B)twice as great.
C)one-half as much.
D)four times as great.
E)one-fourth as much.

Accepted Answer

When two identical resistors are connected in series, the total resistance is the sum of both resistors (R_total = R + R = 2R). When connected in parallel, the total resistance is halved (R_total = R/2). Since the voltage remains constant and according to Ohm's law (V = IR), halving the resistance quadruples the current. Therefore, the total current when the resistors are in parallel is four times as great as when they are in series.

Question 19

A galvanometer has an internal resistance of 200 $\Omega$ and requires a current of 5.0 mA for full-scale deflection.What resistance should be connected in series with this galvanometer to make a voltmeter that reads 25 V at full-scale deflection?
A)2.4 k$\Omega$
B)4.8 k$\Omega$
C)5.0 k$\Omega$
D)5.2 k$\Omega$
E)9.6 k$\Omega$

Accepted Answer

The resistance that needs to be added in series with the galvanometer to create a voltmeter can be calculated using the formula:

R = (V/I) - r

where:
V = full-scale voltage = 25 V
I = full-scale current = 5.0 mA = 0.005 A
r = internal resistance of galvanometer = 200 Ω

Substituting the given values we get:

R = (25/0.005) - 200
R = 5000 - 200
R = 4800 Ω

Therefore, the best choice is B) 4.8 kΩ.

Question 20

If two elements of a circuit are in parallel,they must have the same
A)charge.
B)potential difference across them.
C)resistance.
D)potential difference across them and the same charge.
E)current.

Accepted Answer

When elements are in parallel, they have the same potential difference across them, but they may have different currents and different resistances. The charge on each element may be different since charge is not conserved in an open circuit.

Quiz 25: Electric Current and Direct-Current Circuits

When two identical resistors are connected in series across a battery,the total power dissipated by them is 20 W.If these resistors are connected in parallel across the same battery,the total power dissipated is

Battery A has a relatively high internal resistance,whereas battery B has a low internal resistance.If both batteries provide the same current to some external circuitry,which of the following statements is likely to be true?

When two identical resistors are connected in parallel,the equivalent resistance,compared with that of the same two resistors connected in series,is

When two resistors are connected in series,the equivalent resistance is R_s = 10 $\Omega$ .When they are connected in parallel,the equivalent resistance is R_p = 2.4 $\Omega$ .What are the values of the two resistances?

Two resistors are connected in series across a potential difference.If the current carried by resistor A is I,what is the current carried by B?

In a parallel circuit,

The conservation of charge in an electric circuit is closely related to which of the following?

A resistor of 2 $\Omega$ and another of 3 $\Omega$ are connected in parallel,and this combination is joined in series with a 4- $\Omega$ resistor across a battery.If the current in the 2- $\Omega$ resistor is 2.0 A,the potential drop across the 3- $\Omega$ resistor is

The conservation of energy in an electric circuit is closely related to which of the following?

A 12-V car battery may supply 60 A for 2.5 s in order for the starter motor to start the engine.Calculate how much electrical energy has been used.

You leave your 120-W light bulb on in your room by mistake while you are at school for 8.5 hours.If the price of electrical energy is $0.085 per kilowatt-hour,how much did it cost you?

A galvanometer has an internal resistance of 200 $\Omega$ and requires a current of 5.0 mA for full-scale deflection.What resistance should be connected in parallel with this galvanometer to make an ammeter that reads 10 A at full-scale deflection?

Two resistors R₁ and R₂ are connected in parallel,and this combination is connected in series with a third resistor R₃.If R₁ = 5.0 $\Omega$ ,R₂ = 2.0 $\Omega$ ,and R₃ = 6.0 $\Omega$ ,what is the equivalent resistance of this combination?

If it takes you 5 minutes to dry your hair using a 1200-W hairdryer plugged into a 120-V power outlet,how many Coulombs of charge pass through your hair dryer?

Two resistors are connected in parallel across a potential difference.The resistance of resistor A is twice that of resistor B.If the current carried by resistor A is I,what is the current carried by B?

In your four years at college you dry your hair everyday for 5 minutes with a 1200-W hairdryer.If the average price of electrical energy was $0.085 per kilowatt-hour,how much did it cost you during this time? (Assume 1 year = 365 days.)

Each of three identical electric heaters is rated at 1000 W when operated across 100-V lines.When the three are connected in series across a 120-V line,at what rate is electric energy converted to heat energy? (Neglect variation of resistance with temperature.)

You connect two identical resistors in series across supply lines maintained at a constant potential difference.When you later connect them in parallel across the same supply lines,the total current furnished by the supply lines,compared with the former current,is

A galvanometer has an internal resistance of 200 $\Omega$ and requires a current of 5.0 mA for full-scale deflection.What resistance should be connected in series with this galvanometer to make a voltmeter that reads 25 V at full-scale deflection?

If two elements of a circuit are in parallel,they must have the same