Deck 18: Basic Electric Circuits

Question 1

State Kirchhoff's junction theorem.

Answer 1

The algebraic sum of the currents at any junction is zero.

Question 2

State Kirchhoff's loop theorem.

Answer 2

The algebraic sum of the potential differences across all the elements of any closed loop is zero.

Question 3

For the circuit illustrated in Figure 18-1, write the Kirchhoff current equation for the node labeled A.

Answer 3

I₁ - I₂ + I₃ = 0

Question 4

Write the Kirchhoff loop equation for the entire outside loop (see Figure 18-2)

Question 5

See Figure 18-3. Write the Kirchhoff loop equation for the:

(a) left hand loop in terms of V₁, V₂, R₁, R₂, R₃, R₄, R₅, I₁ and I₂.
(b) right hand loop in terms of V₁, V₂, R₁, R₂, R₃, R₄, R₅, I₁ and I₂.

Question 6

When charging a capacitor with a battery, how would the internal resistance of the battery affect the charging of the capacitor?

Question 7

Why aren't houses wired with outlets in series instead of in parallel?

Question 8

Usually one can touch the terminals of a battery (e.g. 1.5 volts) to equipment in order to guard against the presence of low potentials? (i.e., why are low voltages hazardous in hospitals?)

Question 9

Why do power tools with a plastic case not have a 3-prong plug but metal encased tools have (or should have) 3-prong plugs?

Question 10

When resistors are connected in parallel to a source of emf, the current through each resistor is the same.

Question 11

In a polarized plug, the large slit connects to the hot side and the small slit connects to the neutral, or ground, side.

Question 12

When resistors are connected in series

A) the same power is dissipated in each one.
B) the total effective resistance is reduced.
C) the current flowing in each is the same.
D) the potential difference across each is the same.

Question 13

When two or more resistors are connected in parallel to a battery

A) the total current flowing from the battery equals the sum of the currents flowing through each resistor.
B) the equivalent resistance of the combination is less than the resistance of any one of the resistors.
C) the voltage across each resistor is the same.
D) all of the other choices are true.

Question 14

When two or more resistors are connected in series to a battery

A) the same current flows through each resistor.
B) the total voltage across the combination is the algebraic sum of the voltages across the individual resistors.
C) the equivalent resistance of the combination is equal to the sum of the resistances of each resistor.
D) all of the other choices are true.

Question 15

As more resistors are added in series to a constant voltage source (zero internal resistance), the power supplied by the source

A) does not change.
B) increases for a time and then starts to decrease.
C) decreases.
D) increases.

Question 16

You obtain a 100. W lightbulb and a 50. W light bulb. Instead of connecting them in the normal way, you devise a circuit that places them in series across normal household voltage. Which statement is correct?

A) The 50-W bulb glows more brightly than the 100-W bulb.
B) The 100-W bulb glows brighter than the 50-W bulb.
C) Both bulbs glow at the same reduced brightness.
D) Both bulbs glow at the same increased brightness.

Question 17

A 3. resistor is connected in parallel with a 6. 11eea409_b6c6_d93c_97f4_a5754f0dddc8_TB9720_11 resistor. This pair is then connected in series with a 4. 11eea409_b6c6_d93c_97f4_a5754f0dddc8_TB9720_11 resistor. These resistors are connected to a battery. What will happen if the 3. 11eea409_b6c6_d93c_97f4_a5754f0dddc8_TB9720_11 resistor burns out, i.e., becomes an infinite resistance?

A) The power dissipated in the circuit will increase.
B) The current in the 6. 11eea409_b6c6_d93c_97f4_a5754f0dddc8_TB9720_11 resistor will increase.
C) The current provided by the battery will not change.
D) The current in the 4. 11eea409_b6c6_d93c_97f4_a5754f0dddc8_TB9720_11 resistor will drop to zero.

Question 18

Consider three identical resistors, each of resistance R. The maximum power each can dissipate is P. Two of the resistors are connected in series, and a third is connected in parallel with these two. What is the maximum power this network can dissipate?

A) 2P/3
B) 3P
C) 2P
D) 3P/2
E) P

Question 19

Kirchhoff's junction rule is an example of

A) conservation of charge.
B) conservation of energy.
C) conservation of momentum.
D) conservation of energy and momentum.

Question 20

Kirchhoff's voltage rule for a closed loop is an example of

A) conservation of energy.
B) conservation of charge.
C) conservation of force.
D) conservation of momentum.

Question 21

In Figure 18-4, which of the following equations is true?

A) V₁ - I₁ R₁ - I₂ R₂ + V₂ - I₂ R₃ = 0
B) V₁ + I₁ R₁ - I₂ R₂ - V₂ - I₃ R₄ = 0
C) V₁ - I₁ R₁ + I₂ R₂ - V₂ + I₂ R₃ = 0
D) V₁ I₁ R₁ + I₂ R₂ + V₂ + I₂ R₃ = 0

Question 22

In Figure 18-5, which of the following relations is true?

A) I₁ + I₂ - I₃ = 0
B) I₁- I₂ - I₃ = 0
C) I₁- I₂ + I₃ = 0
D) - I₁ + I₂ + I₃ = 0
E) I₁+ I₂ + I₃ = 0

Question 23

Which of the equations here is valid for the circuit shown in Figure 18-6?

A) 6 - I₁ - 2 I₂ = 0
B) 4 - I₁ + 4 I₃ = 0
C) 2 - 2 I₁ - 2 I₂ - 4 I₃ = 0
D) -2 - I₁ - 2 I₂ = 0
E) 2 - I₁ - 2 I2₃ = 0

Question 24

In a wheatstone bridge (see Figure 18-7) the resistance is varied until no current flows through the Galvanometer (G). Then one knows:

A) R₁ - R₂ = R₃ - R₄
B) R₁ R₄ = R₂ R₃
C) R₁ / R₄ = R₃ / R₂
D) R₁ R₂ = R₃ R₄
E) R₁ + R₂ = R₃ + R₄

Question 25

What is the unit for the quantity RC?

A) seconds
B) volt-Ampere/ohm
C) meters
D) Kg
E) ohms

Question 26

Figure 18-8 is a symbol for which of the following?

A) ammeter
B) galvanometer
C) voltmeter
D) resistor
E) fuse

Question 27

Figure 18-9 is a symbol for which of the following?

A) galvanometer
B) ammeter
C) fuse
D) ground
E) voltmeter

Question 28

Figure 18-10 is a symbol for which of the following?

A) voltmeter
B) galvanometer
C) fuse
D) ammeter
E) ground

Question 29

Increasing the resistance of a voltmeter's series resistance

A) converts it to an ammeter.
B) allows it to measure a larger voltage at full-scale deflection.
C) allows it to measure a smaller voltage at full-scale deflection.
D) enables more current to pass through the meter movement at full-scale deflection.

Question 30

An unknown resistor is wired in series and an ammeter and a voltmeter are placed in parallel across both the resistor and the ammeter. This network is then placed across a battery. If one computes the value of the resistance by dividing the voltmeter reading by the ammeter reading, the value obtained

A) is the true resistance.
B) could be anything. It depends on other factors.
C) is less than the true resistance.
D) is greater than the true resistance.

Question 31

Figure 18-11 is a symbol for which of the following?

A) voltmeter
B) ammeter
C) galvanometer
D) resistor
E) fuse

Question 32

One side of a normal outlet is at 120 V AC, the other side is at

A) -120 V AC.
B) +120 V AC.
C) 120 V AC.
D) 0 V.
E) 240 V.

Question 33

The usual household fuse or circuit breaker is rated at

A) 150 A.
B) 15 A.
C) 1.5 A.
D) 15 mA.
E) 150 mA.

Question 34

The minimum current that will usually kill the average person is

A) 10. A.
B) 0.1 mA.
C) 1. A.
D) 0.01 A.
E) 0.1 A.

Question 35

Current just enough to cause ventricular fibrillation is

A) 1. mA.
B) 1. A.
C) 10. mA.
D) 100. mA.
E) 10. A.

Question 36

A polarized plug

A) has 3 prongs.
B) is asymmetrical.
C) is a grounded plug.
D) may be reversed.

Question 37

The dedicated 3rd wire on a 3 prong plug is connected to

A) ground.
B) a ground fault interrupter.
C) the "hot" wire.
D) a fuse.

Question 38

A "blown" fuse has

A) infinite (very large) resistance.
B) moderate resistance.
C) zero resistance.

Question 39

What different resistances can be obtained by using two 2. $\Omega$ resistors and
one 4. $\Omega$ resistor?

Question 40

A combination of 2.0 $\Omega$ in series with 4.0 $\Omega$ is connected in parallel with 3.0 $\Omega$ . What is the equivalent resistance?

Question 41

What resistance added to 633. $\Omega$ in parallel would produce an equivalent 205. $\Omega$ ?

Question 42

Find the equivalent resistance of the network shown in Figure 18-19 between points A and B:

Question 43

Determine the effective resistance between terminals A and B for the circuit shown in Figure 18-12. Each resistor is 10 ?.

Question 44

R₁ = 5.6 $\Omega$ , R₂ = 5.6 $\Omega$ , R₃ = 14. $\Omega$ , $\varepsilon$ = 6.0 volts

For the circuit shown in Figure 18-13 find:
(a) the total resistance connected to the battery.
(b) the current in each resistor.

Question 45

Examine the circuit shown in Figure 18-14.

(a) Determine the current in each resistor.
(b) Determine the potential difference between points A and B.

Question 46

See Figure 18-15. Given R₁ = 18. $\Omega$ , R₂ = 44. $\Omega$ , R₃ = 33. $\Omega$ , R₄ = 14. $\Omega$ , R₅ = 12. $\Omega$ , V₁ = 18. volts, and V₂ and 12.volts:

(a) determine I₁.
(b) determine I₂.

Question 47

See Figure 18-16. Given R₁ = 50. $\Omega$ , R₂ = 20. $\Omega$ , R₃ = 35. $\Omega$ , R₄ = 10. $\Omega$ , R₅ = 68. $\Omega$ , I₁ and -.111 volts, and I² - 0.142 volts:


(a) determine V₁ and V₂.
(b) determine the potential across R₄.

Question 48

Determine the current and its direction, in each resistor, for the circuit shown in Figure 18-17.

Question 49

An RC circuit with 2.50 $\mu$ F and 7.60 M? includes a 6.00 volt source.
(a) What is the time constant for charging the capacitor?
(b) What voltage is across the capacitor 25. s after charging begins?

Question 50

A 40.0 $\mu$ F capacitor in series with a 5,000. $\Omega$ resistor is charged by a 100. V battery. A neon lamp is connected cross the capacitor (in parallel with it). A neon lamp has a very high resistance before it "fires", i.e., ionizes. When the voltage across it reaches 70. V, it fires and its resistance drops almost instantaneously to zero. It then ceases to conduct once the voltage drops below 70. V. This results in periodically discharging the capacitor. This is the kind of circuit used to make roadside warning lights at construction sites.

Determine the frequency at which the light will blink in the Figure 18-18

Question 51

A galvanometer with a coil resistance of 40. $\Omega$ deflects full scale for a current of 2.0 mA. What series resistance should be used with this galvanometer in order to construct a voltmeter that deflects full scale for 50. V?

Question 52

A 150. $\mu$ A full scale galvanometer is used as a 1.00 A full scale ammeter when shunted by 3.3 m $\Omega$ . What is the coil resistance of the galvanometer?

Question 53

A galvanometer has a coil with a resistance of 24. $\Omega$ . A current of 180. $\mu$ A causes full-scale deflection. If the galvanometer is to be used to construct an ammeter that deflects full scale for 10.0 A, what shunt resistor is required?

Question 54

Consider a galvanometer with full scale sensitivity of 333. $\mu$ A and a coil resistance of 33. $\Omega$ .
(a) What shunt resistance is needed to make a 5.0 A ammeter?
(b) What series resistance is needed to construct a 5.0 volt voltmeter?

Question 55

Three identical resistors are connected in series to a 12-V battery. What is the voltage across any one of the resistors?

A) 0 V
B) 36 V
C) 4 V
D) 3 V
E) 12 V

Question 56

Two 4. resistors are connected in parallel, and this combination is connected in series with 3 https://d2lvgg3v3hfg70.cloudfront.net/TB9720/11eea40a_3ec1_2e8d_97f4_ffd26a7d9b24_TB9720_11. What is the effective resistance of this combination?

A) 7. 11eea40a_3ec1_2e8d_97f4_ffd26a7d9b24_TB9720_11
B) 5. 11eea40a_3ec1_2e8d_97f4_ffd26a7d9b24_TB9720_11
C) 11. 11eea40a_3ec1_2e8d_97f4_ffd26a7d9b24_TB9720_11
D) 1.2 11eea40a_3ec1_2e8d_97f4_ffd26a7d9b24_TB9720_11
E) 4. 11eea40a_3ec1_2e8d_97f4_ffd26a7d9b24_TB9720_11

Question 57

A 3.0 resistor is connected in parallel with a 6.0 11eea40a_3ec1_2e8d_97f4_ffd26a7d9b24_TB9720_11resistor. This combination is connected in series with a 4.0 11eea40a_3ec1_2e8d_97f4_ffd26a7d9b24_TB9720_11 resistor. The resistors are connected to a 12. volt battery. How much power is dissipated in the 3.0 11eea40a_3ec1_2e8d_97f4_ffd26a7d9b24_TB9720_11 resistor?

A) 7.7 W
B) 6 W
C) 2.7 W
D) 12 W
E) 5.3 W

Question 58

A 6.0 and a 12.11eea40a_3ec1_2e8d_97f4_ffd26a7d9b24_TB9720_11resistor are connected in parallel to a 36. V battery. What power is dissipated by the 6.0 11eea40a_3ec1_2e8d_97f4_ffd26a7d9b24_TB9720_11 resistor?

A) 216.W
B) 48. W
C) 24. W
D) 12. W
E) 486. W

Question 59

A 6.0 and a 12. 11eea40a_3ec1_2e8d_97f4_ffd26a7d9b24_TB9720_11 resistor are connected in series to a 36. V battery. What power is dissipated by the 12.0 11eea40a_3ec1_2e8d_97f4_ffd26a7d9b24_TB9720_11 resistor?

A) 12. W
B) 486. W
C) 24. W
D) 48. W
E) 216. W

Question 60

Refer to the portion of a circuit given in Figure 18-20. What is the potential difference V_A - V_B if I = 5.0 Amperes?

A) 45. V
B) 55. V
C) 71. V
D) 35. V
E) 63. V

Question 61

Shown in Figure 18-21 are a few segments of a circuit used to model an infinitely long transmission line. The circuit continues indefinitely in both directions.

What is the value, in amperes, of the current I?

A) 12/125
B) 16/75
C) 8/125
D) 2/25
E) 4/25

Question 62

A fully charged capacitor (37. $\mu$ F) is discharged through a resistor (1000. ohms). If the voltage reduced to 7.6 volts after just 20. ms, what was the original potential on the capacitor?

A) 16. volts
B) 13. volts
C) 11. volts
D) 9.0 volts
E) 8.0 volts

Question 63

A 1234. pF capacitor and a 5.6 × 10⁶ ohm resistor are connected in series to 78. volts EMF. Approximately how long does it take the capacitor to become almost fully charged?

A) 0.1 ms
B) 1. $\mu$ s
C) 0.01 s
D) 1. ps
E) 1. s

Question 64

A 2.0 $\mu$ F capacitor is charged through a 50,000. resistor. How long does it take for the capacitor to reach 90% of full charge?

A) 2.19 s
B) 0.23 s
C) 2.3 s
D) 9.1 s
E) 0.9 s

Question 65

A 4.0 $\mu$ F capacitor is charged to 6.0 V. It is then connected in series with a 3.0 M resistor and connected to a 12. V battery. How long after being connected to the battery will the voltage across the capacitor be 9.0 V?

A) 11. s
B) 5.5 s
C) 12. s
D) 8.3 s
E) 17. s

Question 66

A 4.0 M resistor is connected in series with a 0.5 $\mu$ F capacitor. The capacitor is initially uncharged. The RC combination is charged by a 9.0 V battery. What is the change in voltage between t = RC and t = 3RC?

A) 11.4 V
B) 2.88 V
C) 8.81 V
D) 5.70 V
E) 7.59 V

Question 67

A galvanometer with a coil resistance of 80. deflects full scale for a current of 2.00 mA. What series resistance is required to convert it to a voltmeter reading full scale for 200. V?

A) 100.02 k11eea40a_e302_9700_97f4_89f651598bd8_TB9720_11
B) 0.800 m11eea40a_e302_9700_97f4_89f651598bd8_TB9720_11
C) 13.2 M11eea40a_e302_9700_97f4_89f651598bd8_TB9720_11
D) 100. k11eea40a_e302_9700_97f4_89f651598bd8_TB9720_11
E) 99.92 k11eea40a_e302_9700_97f4_89f651598bd8_TB9720_11

Question 68

My electric razor operates on 120. v and requires 3.0 Amperes. How much current comes out after delivering 360. watts of power?

A) 2.4 A
B) 3.0 A
C) 0. A
D) 40. A
E) 1.2 A