intro
Question 1:
What is the current value for an open circuit?
Topic: Concepts of Current and Circuit Theory
Correct Answer: A) Zero
- In the context of electrical circuits, an open circuit means there is no continuity or the path is broken.
- Consequently, no current can flow, so the current value is zero.
- Hence, the correct answer is A, "Zero".
Question 2:
If a 90C charge passes through a wire over the span of an hour, what is the current in the wire?
Topic: Understanding Current and Charge
Correct Answer: C) 25 mA
- I = Q/T, where Q is charge and T is time, defines current as the rate at which electric charge flows.
- In this case, I = 90C/3600s = 0.025A or 25 mA.
- Thus, the correct answer is C, "25 mA".
Question 3:
The potential difference across a battery's terminals is 2.2 V when open circuited. When connected to a 5.0 ohm resistance, the potential drops to 1.8 V. What is the battery's current?
Topic: Concepts of Potential Difference and Current
Correct Answer: A) 0.36A
- When current is drawn from a battery, the terminal voltage decreases.
- The current in the 5 Ohm resistance is I = V/R = 1.8V/5Ohm = 0.36A
- This means that the 0.36A internal resistance must be the cause of the voltage drop from 2.2V to 1.8V.
- Therefore, the correct answer is A, "0.36A".
Question 4:
A car battery has a rating of 80Ah. What does the ampere-hour unit represent?
Topic: Understanding Units of Measurement in Electricity
Correct Answer: D) Charge
- Ampere-hour is a unit that measures electric charge, calculated as the product of current (in amperes) and time (in hours).
- Using Q = I×t, charge can be calculated.
- Thus, the correct answer is D, "Charge".
Question 5:
In a circuit with two unequal resistances in parallel, which statement is true?
Topic: Understanding Resistances in Parallel Circuits
Correct Answer: C) The potential difference across each is the same
- In parallel circuits, the potential difference (voltage) across each component is the same.
- Therefore, despite the resistances being unequal, their potential difference remains the same.
- Thus, the correct answer is C, "The potential difference across each is the same".
Question 6:
There are two resistors of value R and 3R connected in parallel to a voltage source V. What is the voltage drop across the 3R resistance?
Topic: Voltage in Parallel Circuits
Correct Answer: A) The same as that across R
- In parallel circuits, the voltage drop across each component is the same, regardless of the resistance value.
- Therefore, the voltage drop across the 3R resistance is the same as that across R.
- Thus, the correct answer is A, "The same as that across R".
Question 7:
What is the graphical representation of Ohm’s Law?
Topic: Ohm’s Law and Its Graphical Representation
Correct Answer: D) Straight Line
- According to Ohm's Law, conductor current is directly proportional to voltage across a conductor.
- This relationship forms a straight line when plotted on a graph with voltage (V) on the y-axis and current (I) on the x-axis.
- Thus, the correct answer is D, "Straight Line".
Question 8:
What phenomenon occurs in the surrounding area due to the presence of an electric current?
Topic: Effects of Electric Current
Correct Answer: C) Generation of a Magnetic field
- A significant characteristic of electric current is that it always generates a magnetic field in its vicinity.
- This phenomenon is employed in various applications, such as electromagnets and electric motors.
- Hence, the correct answer is C, "Generation of a Magnetic field".
Question 9:
Two bulbs with power ratings P1 watt and P2 watt respectively and both rated at V volts, are connected in series across a voltage of V volts. What will the total power be?
Topic: Power in Series Circuit
Correct Answer: D) P1P2 / (P1 + P2)
- When two bulbs are connected in series across a voltage source, the total power is given by the formula P = P1P2 / (P1 + P2).
- Essentially, a series circuit has a total resistance equal to the sum of its individual resistances.
- Therefore, the correct answer is D, "P1P2 / (P1 + P2)".
Question 10:
What is the SI unit of resistivity?
Topic: Basic Units in Electricity
Correct Answer: C) Ohm meter (Ω. m)
- The SI system defines the unit of resistivity as the Ohm meter, represented as Ω. m.
- This unit quantifies how strongly a given material opposes the flow of electric current.
- Therefore, the correct answer is C, "Ohm meter (Ω. m)".
Question 11:
What factor influences the specific resistance of a wire?
Topic: Wire Resistance Factors
Correct Answer: C) The material the wire is made of
- Specific resistance, also known as resistivity, is a material property that depends on the type of material used in the wire, not its length or radius.
- Temperature can also influence resistivity.
- Hence, the correct answer is C, "The material the wire is made of".
Question 12:
According to Ohm's Law, the current "I" flowing through a conductor is directly proportional to which of the following?
Topic: Ohm's Law and Current Flow
Correct Answer: A) Voltage (V)
- Ohm's Law states that the current "I" in a conductor is directly proportional to the voltage "V" across it, assuming constant temperature and material.
- V = IR, where R is the resistance, represents the relationship.
- Thus, the correct answer is A, "Voltage (V)".
Question 13:
If both the length and diameter of a wire are doubled, what will happen to its resistance?
Topic: Resistance and Wire Dimensions
Correct Answer: B) It will be halved
- Physicists believe that doubling a wire's length will result in doubling its resistance.
- However, if the diameter of the wire is doubled, the resistance will decrease by a factor of 4.
- Therefore, the overall change in resistance will be a halving (2/4 = 1/2).
- Hence, the correct answer is B, "It will be halved".
Question 14:
An object is charged to a value of 5 micro coulombs. How can this charge be represented in base units?
Topic: Electric Charge Conversion
Correct Answer: A) 5 × 10-6 ampere second
- Charge (q) can be calculated using the formula q = I × t, where I is current and t is time.
- An ampere second is the base unit used to represent charge.
- Thus, the correct answer is A, "5 × 10-6 ampere second".
Question 15:
Three resistors, each of value 'R', are arranged as depicted in an unshown figure. What is the aggregate resistance between points 'X' and 'Y'?
Topic: Series Resistance Calculation
Correct Answer: B) 3R
- As a result of connecting resistors in series, the total resistance (RTOT) can be computed as the addition of the separate resistances: RTOT = R1 + R2 + R3 ... and so on.
- In this case, all resistors have the same resistance 'R', so the total resistance will be 3R.
- Hence, the correct answer is B, "3R".
Question 16:
Three resistors with resistance values of 2 ohms, 3 ohms, and 6 ohms are wired in parallel. What is their combined resistance?
Topic: Parallel Resistance Calculation
Correct Answer: B) 1Ω
- The total resistance of parallel resistors can be calculated using the formula 1/RTOT = 1/R1 + 1/R2 + 1/R3... and so on.
- Given resistances are R1 = 2 ohm, R2 = 3 ohm, R3 = 6 ohm in this scenario.
- Based on the calculation with the given values, the total resistance comes out to be 1Ω.
- Therefore, the correct answer is B, "1Ω".
Question 17:
Kirchhoff’s second rule is associated with which law of conservation?
Topic: Kirchhoff’s Laws and Conservation Laws
Correct Answer: C) Energy
- Kirchhoff’s second law, also known as Kirchhoff's Voltage Law (KVL), is a statement of the conservation of energy principle for electrical circuits.
- It states that the sum of the electric potential differences (voltages) in any closed loop or mesh in a network is always equal to zero.
- This is essentially a restatement of the conservation of energy. Therefore, the correct answer is C, "Energy".
Question 18:
If a wire with a consistent cross-sectional area is divided into two equal parts, what will be the resistivity of each half?
Topic: Resistivity and Material Properties
Correct Answer: C) Remains the same
- Resistivity is a fundamental property of the material of the wire. It does not depend on the size or shape of the wire, but only on the substance it is made of.
- Therefore, even if the wire is cut into two equal halves, the resistivity of each half will remain the same.
- Hence, the correct answer is C, "Remains the same".
Question 19:
What impact does a rise in temperature have on a substance's resistance?
Topic: Temperature and Resistance
Correct Answer: C) Resistance can either increase or decrease
- The effect of temperature on resistance depends on the type of material.
- For conductors, resistance usually increases with temperature, whereas for semiconductors and insulators, resistance typically decreases.
- Hence, an increase in temperature can cause either an increase or decrease in resistance, depending on the substance.
- Therefore, the correct answer is C, "Resistance can either increase or decrease".
Question 20:
In the context of resistances, which of the following is true about series and parallel connections?
Topic: Characteristics of Series and Parallel Resistances
Correct Answer: D) In series: Uniform current; In parallel: Uniform voltage.
- Each resistor in a series connection flows the same current.
- Conversely, when resistances are arranged in parallel, the voltage across each resistor remains constant.
- Therefore, the correct response is D, "In series: Uniform current; In parallel: Uniform voltage".
MCQs 21:
Which among the following is a non-Ohmic conductor?
Topic: Ohmic and Non-Ohmic Conductors
Correct Answer: B) Filament of a light bulb
- An Ohmic conductor is a material that abides by Ohm's law, meaning the current through it is directly proportional to the voltage across it.
- However, the filament of a light bulb, being a non-Ohmic conductor, doesn't strictly adhere to Ohm's law, as its resistance varies with voltage and temperature.
- Hence, the correct answer is B, "Filament of a light bulb".
MCQs 22:
What is the correlation between the resistance of a copper wire and its physical characteristics?
Topic: Resistance and Physical Properties
Correct Answer: D) Both A and B.
- As per Ohm's Law, resistance of a wire increases inversely with its length and directly proportional to the area of its cross-section.
- This applies to all conductive materials, including copper. The amount of current in the wire does not affect its resistance.
- Therefore, the correct answer is D, "Both A and B".
Question 23:
What is the potential range of the actual value for a 1000-ohm resistor with a tolerance of 20 percent?
Topic: Resistor Tolerance
Correct Answer: B) Between 800 and 1200 ohms
- Resistance tolerance refers to the range of deviations from the nominal value of a resistor.
- A tolerance of 20 percent means the actual resistance could be anywhere within 20 percent above or below the stated value of 1000 ohms.
- Therefore, the correct answer is B, "Between 800 and 1200 ohms".
Question 24:
Under what condition would the resistance of a metal wire become eight times its original value?
Topic: Resistance Factors
Correct Answer: D) If the length is doubled and the radius is halved
- According to Ohm's law, resistance increases with length and decreases with radius.
- If the length of the wire is doubled and the radius is halved, the resistance will increase by a factor of eight.
- Thus, the correct answer is D, "If the length is doubled and the radius is halved".
Question 25:
An electrical current of 5A is equivalent to which of the following?
Topic: Electric Current
Correct Answer: C) 5 coulombs per second
- A current measures how fast an electric charge flows, and it is measured in amperes (A).
- Therefore, 1 ampere is equivalent to 1 coulomb per second.
- Consequently, the correct answer is C, "5 coulombs per second".
Question 26:
What would be the total resistance if 'N' number of resistors, each having resistance 'R', are connected in series?
Topic: Total Resistance in Series
Correct Answer: A) NR
- The total resistance of a series of resistors (R(total)) is equal to the sum of the individual resistances (R1 + R2 +...+ RN).
- In this case, all resistors have the same resistance, R, thus total resistance will be NR.
- Consequently, the correct answer is A, "NR".
Question 27:
Which principle is demonstrated by the statement "The total current entering a junction equals the total current leaving the junction"?
Topic: Current Conservation Principle
Correct Answer: B) Conservation of charge
- The idea that the sum of currents flowing into a point must equal the sum of currents flowing out of the point represents the principle of charge conservation.
- This is because charge cannot be created or destroyed, it can only be transferred.
- Thus, the correct answer is B, "Conservation of charge".
Question 28:
What happens to the power dissipated in a resistor if the current flowing through it is tripled?
Topic: Power Dissipation in Resistors
Correct Answer: D) Increases by 9 times.
- A resistor's power dissipation is directly proportional to its squared current, as shown by the equation P=I2R.
- Therefore, if the current is tripled (increased by 3 times), the power dissipated will increase by 3² (9 times).
- Hence, the correct answer is D, "Increases by 9 times".
Question 29:
What is the expression for the heat generated by a current 'I' flowing through a wire with resistance 'R'?
Topic: Heat Generation in a Wire
Correct Answer: B) I²Rt
- The power dissipated in a wire due to the flow of current is given by the formula P = I²R.
- To convert this power into energy (or heat), we must multiply it by the time for which current flows. Therefore, the heat produced equals I²Rt.
- As a result, the correct answer is B, "I²Rt".
Question 30:
A person possesses five resistors, each with a resistance of 1/5 ohm. By combining them, what is the least amount of resistance that can be achieved?
Topic: Minimum Resistance
Correct Answer: B) 1/25 Ω
- A parallel connection of resistors decreases the total resistance. This is because the total current has more paths to follow, reducing the overall resistance.
- In this scenario, five resistors each of 1/5 ohm are connected in parallel, resulting in the minimum resistance of 1/25 ohm.
- Thus, the correct answer is B, "1/25 Ω".
Question 31:
A person has five resistors, each of value 1/5 ohm. The maximum resistance he can get by combining them is?
Topic: Maximum Resistance
Correct Answer: A) 1 Ω
- A series connection of resistors increases the total resistance.
- This is because the current has to flow through each resistor in turn, resulting in increased resistance.
- In this scenario, five resistors each of 1/5 ohm are connected in series, resulting in the maximum resistance of 1 ohm.