Quiz 3 For Unit Exam
Electrical Circuits
Questions and Answers
- 1.
A flow of electrons from one atom to another is called
- A.
Voltage
- B.
Current
- C.
Charge
- D.
Inductance
Correct Answer
B. CurrentExplanation
Current refers to the flow of electric charge (electrons) from one atom to another. It is the movement of these charged particles through a conductor, such as a wire. Current is measured in amperes (A) and is a fundamental concept in electrical circuits. Voltage, on the other hand, refers to the potential difference that drives the current flow. Charge refers to the property of matter that causes it to experience a force in an electric field. Inductance is a property of an electrical circuit that opposes changes in current flow.Rate this question:
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- 2.
The unit of measure used to express the difference in the number of charges at two physically different points in a circuit is the:
- A.
Volt
- B.
Coulomb
- C.
Ampere
- D.
Siemens
Correct Answer
A. VoltExplanation
The unit of measure used to express the difference in the number of charges at two physically different points in a circuit is the volt. The volt is a derived unit of electric potential difference, which represents the amount of work needed to move a unit of electric charge between two points. It is commonly used to measure voltage, which is the driving force that pushes electric charges through a circuit. The other options, coulomb, ampere, and siemens, are units of charge, current, and conductance, respectively, and do not directly measure the difference in charges between two points.Rate this question:
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- 3.
The minimum amount of current that could potentially kill a human is usally suggested to be:
- A.
1 mA
- B.
15 mA
- C.
500 mA
- D.
1 A
Correct Answer
B. 15 mAExplanation
The minimum amount of current that could potentially kill a human is usually suggested to be 15 mA. This is because at this level of current, the heart can go into ventricular fibrillation, a condition where the heart beats irregularly and cannot pump blood effectively. Ventricular fibrillation can lead to cardiac arrest and ultimately death if not treated immediately. Current levels below 15 mA may still cause harm, but the risk of fatality is significantly higher at or above this threshold.Rate this question:
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- 4.
Which of the following is NOT a form of Ohm's Law?
- A.
I=VR
- B.
R=V/I
- C.
V=IR
- D.
I=V/R
Correct Answer
A. I=VRExplanation
The equation I=VR is not a form of Ohm's Law. Ohm's Law states that the current flowing through a conductor is directly proportional to the voltage applied across it and inversely proportional to the resistance of the conductor. The correct forms of Ohm's Law are R=V/I, V=IR, and I=V/R.Rate this question:
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- 5.
The milliampere has a value that is:
- A.
One million times larger than a microampere
- B.
One thousand times larger than an ampere
- C.
One millionth of an ampere
- D.
One thousandth of an ampere
Correct Answer
D. One thousandth of an ampereExplanation
The milliampere is a unit of electric current that is equal to one thousandth of an ampere. This means that a milliampere is a smaller unit than an ampere.Rate this question:
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- 6.
In any electrical circuit, an increase in current flow is created when:
- A.
The source voltage is decreased
- B.
The resistance is increased
- C.
The resistance is decreased
- D.
Either C or D above
Correct Answer
D. Either C or D aboveExplanation
An increase in current flow in an electrical circuit can be caused by either decreasing the resistance or decreasing the source voltage. When the resistance is decreased, there is less opposition to the flow of electrons, allowing more current to pass through the circuit. Similarly, when the source voltage is decreased, there is a smaller potential difference pushing the electrons, resulting in an increase in current flow. Therefore, either decreasing the resistance or decreasing the source voltage can lead to an increase in current flow.Rate this question:
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- 7.
What is the quantity of heat, in watts given off when a 5 ohm resistor has 10 volts applied to its terminals?
- A.
20
- B.
50
- C.
250
- D.
500
Correct Answer
A. 20Explanation
When a voltage of 10 volts is applied to a resistor with a resistance of 5 ohms, we can use Ohm's law (V = IR) to find the current flowing through the resistor. The current can be calculated as 10 volts divided by 5 ohms, which equals 2 amps.
To find the quantity of heat given off by the resistor, we can use the formula P = IV, where P is power in watts, I is current in amps, and V is voltage in volts. Plugging in the values, we get P = 2 amps * 10 volts = 20 watts. Therefore, the correct answer is 20.Rate this question:
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- 8.
A series ciruit has a current flow of 50 mA and its resistance is 100 ohms. The source voltage is:
- A.
5 V
- B.
20 V
- C.
500 V
- D.
2 V
Correct Answer
A. 5 VExplanation
In a series circuit, the total resistance is equal to the sum of individual resistances. Using Ohm's law (V = I * R), we can calculate the source voltage. Given that the current flow is 50 mA (0.05 A) and the resistance is 100 ohms, the source voltage can be calculated as V = 0.05 A * 100 ohms = 5 V. Therefore, the correct answer is 5 V.Rate this question:
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- 9.
When a EMF of 2KV is applied to a 0.15 M ohm resistance, the current flow will be about:
- A.
830 mA
- B.
133 mA
- C.
83 mA
- D.
13 mA
Correct Answer
D. 13 mAExplanation
Ohms Law I=V/RRate this question:
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- 10.
An electrical appliance has 300 ohms of resistance. What is its current flow when connected to a 120 V source
- A.
25 mA
- B.
25 A
- C.
400 mA
- D.
None of the above
Correct Answer
C. 400 mAExplanation
I = V divided by RRate this question:
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- 11.
The rule for voltage drops in series circuit is:
- A.
The sum of the voltage drops equals the applied voltage
- B.
All voltage drops are equal
- C.
The smallest resistance has the largest voltage drop.
- D.
The voltage drop across the largest resistance equals the applied V.
Correct Answer
A. The sum of the voltage drops equals the applied voltageExplanation
In a series circuit, the total voltage supplied by the power source is divided among the different components. According to Ohm's Law, the voltage drop across each component is directly proportional to its resistance. Therefore, the sum of the voltage drops across all the components in a series circuit will equal the applied voltage. This is because the total resistance in a series circuit is the sum of the individual resistances, and the voltage drop across each component is determined by its resistance.Rate this question:
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- 12.
A series circuit consists of 7 lamps of equal value. When one lamp filament fails (burns out) and is "open" the rest:
- A.
Will stay lit
- B.
Will not stay lit
- C.
Will also fail and be "open"
- D.
None of these
Correct Answer
B. Will not stay litExplanation
Relate this to the old christmas lights...when one bulb dies they all go out!Rate this question:
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- 13.
If the applied voltage is increased in a series circuit:
- A.
The total resistance will decrease and current will stay the same
- B.
Current and resistance will both increase
- C.
Current will increase and the resistance will stay the same
- D.
Current and resistance will both decrease
Correct Answer
C. Current will increase and the resistance will stay the sameExplanation
When the applied voltage in a series circuit is increased, the current flowing through the circuit will increase. This is because the increase in voltage causes a greater potential difference across the circuit, which in turn leads to a higher current. However, the resistance in the circuit will remain the same. Resistance is determined by the physical properties of the components in the circuit and is not affected by changes in the applied voltage. Therefore, the correct answer is that the current will increase and the resistance will stay the same.Rate this question:
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- 14.
With two equal resistances in series across a 90 volt battery, the voltage across each resistor equals:
- A.
30 Volts
- B.
45 Volts
- C.
90 Volts
- D.
180 Volts
- E.
It is impossible to determine the voltages unless the resistor values are known.
Correct Answer
B. 45 VoltsExplanation
V = I * RRate this question:
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- 15.
An ammeter should always be connected
- A.
Across the load
- B.
In series with ground
- C.
In series with the part of the circuit under test
- D.
In parallel with the power source
Correct Answer
C. In series with the part of the circuit under testExplanation
An ammeter should always be connected in series with the part of the circuit under test. This is because an ammeter is used to measure the current flowing through a circuit, and to accurately measure the current, it needs to be placed in the path of the current. Connecting it in series with the part of the circuit under test allows the ammeter to measure the current passing through that specific part of the circuit. Connecting it in parallel with the power source or in series with ground would not provide an accurate measurement of the current in the circuit.Rate this question:
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- 16.
An ideal voltmeter would have
- A.
A very low resistance
- B.
A very high resistance
- C.
Zero resistance
- D.
A passion pink carrying case that matches your shoes
Correct Answer
C. Zero resistanceExplanation
An ideal voltmeter would have zero resistance because it should not draw any current from the circuit being measured. If the voltmeter has resistance, it will affect the voltage being measured and give inaccurate readings. Therefore, zero resistance is desirable in an ideal voltmeter to ensure accurate voltage measurements without any interference or disturbance to the circuit.Rate this question:
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