intro
Question 1:
Which of the following is the standard unit for resistance in SI units?
Topic: Basic Electricity
Correct Answer: C) Resistance
- SI units are internationally accepted units for measurement.
- In the case of electrical resistance, the standard unit is "Ohm".
- It signifies the opposition encountered by electric current when it passes through a substance.
- Therefore, the correct answer is C, "Resistance".
Question 2:
What happens to the resistance of a wire if its length is tripled?
Topic: Electrical Resistance and Conductance
Correct Answer: D) It becomes nine times (9R)
- A wire's resistance increases as its length increases.
- Specifically, if a wire is stretched into triple its original length, the resistance increases by the square of that factor.
- Hence, in this case, the resistance becomes nine times (9R).
Question 3:
At absolute zero, how much resistance does a conductor have?
Topic: Superconductivity and Resistance
Correct Answer: B) Zero
- At absolute zero, a conductor becomes a superconductor.
- In a superconductor, the resistance is essentially zero as the material allows the electric current to flow without any opposition.
- As such, the correct answer is B, "Zero".
Question 4:
According to Ohm's law, what does the constant V/I represent?
A) Voltage
B) Current
C) Power
D) Resistance
Topic: Ohm's Law and Electrical Resistance
Correct Answer: D) Resistance
- A conductor flows current between two points directly proportional to its voltage according to Ohm's law.
- Resistance is the constant V/I, which equals V = IR (where V denote voltage, I denote current, and R is resistance).
Question 5:
What is the resistance characteristic of a superconductor?
Topic: Superconductivity and Electrical Resistance
Correct Answer: C) Zero
- Superconductors display a unique characteristic of having zero electrical resistance. This means that electrons can move through these materials without losing any energy to heat.
Question 6:
What unknown electrical quantity is typically measured using a Wheatstone bridge?
Topic: Measurement and Instrumentation
Correct Answer: C) Resistance
- To measure an unknown electrical resistance, Wheatstone bridges are widely used. In this case, the unknown component is included in one leg of a bridge circuit.
Question 7:
What happens to the resistance of a 100 Ω wire when it's folded onto itself?
Topic: Electrical Resistance and Conductance
Correct Answer: D) Becomes 400 ohms
- As the length of a resistor is doubled and its cross-sectional area is halved, the combined effect results in the resistance quadrupling.
- So, for a wire with an initial resistance of 100 Ω, when folded onto itself, the new resistance becomes 400 Ω.
- Thus, the correct answer is D, "Becomes 400 ohms".
Question 8:
What is the typical temperature coefficient sign for thermistors?
Topic: Thermistors and Temperature Coefficients
Correct Answer: A) Always negative
- Thermistors, especially those with a high negative temperature coefficient, are incredibly accurate for low temperature measurements, particularly around 10K.
- Meaning, the correct answer is A, "Always negative".
Question 9:
The ratio of the lengths of two wires of the same material is 2:3, while their diameters are 1:2. What would be the resistance ratio between them?
Topic: Electrical Resistance and Conductance
Correct Answer: A) 8:3
- In wires, resistance proportionally increases with length and decreases with cross-sectional area.
- From the given ratios, we can derive the resistance ratio as 8:3.
- Hence, the correct answer is A, "8:3".
Question 10:
Which instrument is commonly employed to estimate the internal resistance of a cell?
Topic: Measurement and Instrumentation
Correct Answer: D) Potentiometer
- A Potentiometer serves several functions such as acting as a potential divider, measuring the unknown EMF of a cell, comparing the unknown EMFs of two cells, and measuring the internal resistance of a cell.
- Therefore, the correct answer is D, "Potentiometer".
Question 11:
What is the term for the fractional alteration in resistivity for each degree of temperature change?
Topic: Resistivity and Temperature Coefficients
Correct Answer: C) Temperature coefficient of resistivity
- The fractional variation in resistivity per unit change in temperature is defined as the temperature coefficient of resistivity.
- This governs how the resistivity of a material changes with temperature.
Question 12:
How many resistors are incorporated in a Wheatstone bridge?
Topic: Wheatstone Bridge and Resistors
Correct Answer: C) 4
- Wheatstone bridges are electrical circuits used to measure resistance precisely.
- It typically comprises four resistors.
Question 13:
In electrical terms, what is the equivalent of mass in mechanics?
Topic: Electrical-Mechanical Analogy
Correct Answer: A) Inductance
- Drawing from the mechanical-electrical analogy, where displacement corresponds to charge and force corresponds to voltage, we find that the electrical equivalent of mass is inductance.
- Hence, the correct answer is A, "Inductance".
Question 14:
If three identical resistors, each of 15Ω, are interconnected in a parallel configuration, what would be the equivalent resistance?
Topic: Electrical Resistance and Parallel Circuits
Correct Answer: A) 5Ω
- In a parallel circuit configuration, the equivalent resistance (Rp) is given by the formula Rp = R/n, where R is the resistance of one resistor and n is the number of parallel resistors.
- Substituting the provided values into the equation, we get Rp = 15Ω/3 = 5Ω.
- Consequently, the correct answer is A, "5Ω".
Question 15:
What are the units of the temperature coefficient of resistivity?
Topic: Resistivity and Temperature Coefficients
Correct Answer: B) K^-1
- The temperature coefficient of resistivity represents how resistivity changes with temperature, and its unit is reciprocal temperature (inverse Kelvin), denoted as K^-1.
Question 16:
Given a circuit diagram with three resistors (R1, R2, and R3) arranged in series where R1 > R2 > R3, rank them according to the current flowing through them, from least to greatest.
Topic: Electrical Resistance and Series Circuits
Correct Answer: D) All have the same current
- Regardless of the resistance value of the resistors, the same current flows through them all in a series circuit. This is because there is only one path for the current to flow.
Question 17:
Consider four wires made of the same material, each having different lengths and radii. Which wire will demonstrate the highest resistance?
Topic: Electrical Resistance and Wire Dimensions
Correct Answer: C) l = 100cm, r = 0.5mm
- A wire's resistance depends directly on its length and inversely on its radius squared. This is represented by the formula R = ρL/πr², where ρ is resistivity, L is length, and r is radius.
- The wire with the greatest length and the smallest radius will have the highest resistance, in this case, l = 100cm and r = 0.5mm. Therefore, the correct answer is C.
Question 18:
What type of energy is primarily converted into electrical energy by thermocouples?
Topic: Energy Conversion in Thermocouples
Correct Answer: A) Thermal energy
- Thermocouples are devices that convert temperature differences into electrical voltage using the Seebeck effect.
- Therefore, the primary energy conversion happening in thermocouples is from thermal energy to electrical energy. Hence, the correct answer is A, "Thermal energy".
Question 19:
In a domestic electrical circuit, all appliances are linked in parallel between the line and neutral wires. What is the primary reason for this configuration?
Topic: Domestic Electrical Wiring and Parallel Configuration
Correct Answer: C) To allow for different currents but maintain the same potential difference
- Home appliances are wired in parallel to allow them to operate independently of each other. Turning one appliance on or off doesn't affect the operation of others.
- Another advantage is that the potential difference across each appliance is the same and equals the supply voltage, ensuring correct power delivery to each appliance.
- This setup allows for different currents but the same potential difference.
- Therefore, the correct answer is C.
Question 20:
Three resistors, each with a resistance of 4 Ohms, are arranged in the shape of a triangle. What is the resistance across any two points?
Topic: Resistance Calculation in a Triangular Configuration
Correct Answer: C) 8/3 Ohms
- Resistors arranged in a triangular or delta configuration can be analyzed using specific formulas.
- The equivalent resistance Req, across any two points in a triangle consisting of equal resistances, is given by Req = 2/3 x R, where R is the resistance of each side.
- In this case, R = 4 Ohms, so Req = 8/3 Ohms.
- This formula is specific to a triangular arrangement of resistors.
Question 21:
Which of the following can be used as a unit of energy?
Topic: Units of Energy
Correct Answer: A) Watt-second
- There are many ways to express energy as a physical quantity.
- A Watt-second (W.s) is one of the possible units of energy, where one Watt-second is equal to one joule. It represents the amount of energy consumption or generation when a one-watt electrical device is used for one second. Hence, the correct answer is A, "Watt-second".
Question 22:
What is the approximate drift velocity?
Topic: Drift Velocity
Correct Answer: B) 10-3ms-1
- An electric field causes charged particles, such as electrons, to achieve drift velocity, which is their average velocity.
- Typically, in conductors, the drift velocity is on the order of 10-3ms-1. Therefore, the correct answer is B.
Question 23:
When a battery in a circuit where current is flowing is connected directly to a voltmeter, what will it measure?
Topic: Voltmeter Measurements
Correct Answer: B) Terminal voltage difference
- A voltage meter measures the electric potential difference between two points in an electric circuit.
- When a voltmeter is connected directly to a battery in a circuit where current is flowing, it measures the terminal voltage difference. However, when no current is flowing, the voltmeter reads the electromotive force (emf). Therefore, the correct answer is B, "Terminal voltage difference".
Question 24:
The resistance R provided by a wire with length L and cross-sectional area A is represented by?
Topic: Resistance Measurements
Correct Answer: A) ρL/A
- Wire resistance is determined by Ohm's law, which determines its direct proportionality to its length and inverse proportionality to its cross-sectional area.
- Hence, the formula for resistance is R = ρL/A, where ρ is the resistivity of the material. Therefore, the correct answer is A, "ρL/A".
Question 25:
Which of the following exhibits a positive temperature coefficient?
Topic: Temperature Coefficients
Correct Answer: D) Iron
- The temperature coefficient is a measure of how much a material's resistance changes with temperature.
- Metallic conductors, such as iron, typically have a positive temperature coefficient, meaning their resistance increases as the temperature rises.
- Hence, the correct answer is D, "Iron".
Question 26:
A technician has a set of 10 resistors, each with a resistance of 0.1Ω. What are the maximum and minimum resistances they can achieve by combining these resistors?
Topic: Resistor Combinations
Correct Answer: C) 1Ω and 0.01Ω respectively
- When resistors are combined in series, the total resistance is the sum of their resistances.
- Thus, in this case, the maximum resistance is 10 * 0.1Ω = 1Ω.
- It is the reciprocal of the reciprocal of each of the individual resistances that is the reciprocal of the total resistance for parallel combinations.
- Hence, the minimum resistance here is 0.1Ω/10 = 0.01Ω.
Question 27:
In practical application, the potentiometer draws:
Topic: Potentiometer Characteristics
Correct Answer: D) No current
- A potentiometer is utilized in circuits primarily for measuring potential difference or internal resistance of a cell.
- Under balanced conditions, where we get an accurate measurement, the potentiometer draws no current. Thus, the correct answer is D, "No current".
Question 28:
What would be the total resistance in a circuit with three resistors, each of 9Ω, connected in parallel?
Topic: Equivalent Resistance in Parallel Circuits
Correct Answer: B) 3Ω
- In a parallel circuit, the inverse of the equivalent resistance equals the sum of the inverses of the individual resistances.
- Therefore, in this scenario, the equivalent resistance Re = R/n = 9/3 = 3Ω. Hence, the correct answer is B, "3Ω".
Question 29:
Which of the following devices leverages the heating effect of electric current?
Topic: Heating Effect of Electric Current
Correct Answer: D) All of the above
- The resistance in a conductor generates heat when an electric current flows through it. This is known as the heating effect of electric current.
- Various everyday devices utilize this effect. For instance, an electric bulb produces light when its filament gets heated due to the current. Similarly, electric irons and heaters function on the same principle. Hence, the correct answer is D, "All of the above".
Question 30:
How can seven 2Ω resistors be arranged to obtain a net resistance of 22/5 Ω?
Topic: Resistor Arrangements
Correct Answer: A) 5 in parallel, 2 in series
- Resistors can be organized in two main ways - series and parallel.
- In series, resistances simply add up, while in parallel, the reciprocal of total resistance is the sum of reciprocals of individual resistances.
- Given seven 2Ω resistors and the target resistance of 22/5 Ω, the arrangement that fulfills this condition is 5 resistors in parallel and 2 in series. Thus, the correct answer is A, "5 in parallel, 2 in series".
Question 31:
What does the area under the curve represent in an Ohm's Law graph?
Topic: Ohm's Law Graph Interpretation
Correct Answer: C) Electrical power
- Ohm's Law relates the voltage across a conductor to the current flowing through it, with the resistance being the constant of proportionality.
- In a graph plotting current (I) versus voltage (V), the area under the curve represents the product of these two quantities (I x V).
- This product is the power consumed by the electrical component. Therefore, the correct answer is C, "Electrical power".
Question 32:
What would be the energy consumed by an electrical iron, labelled as 20 volts 500 W, if it is used continuously for 24 hours?
Topic: Energy Consumption
Correct Answer: A) 12
- The energy consumption of electrical appliances depends on their power rating and the time they're used.
- The given iron has a power rating of 500W and is used for 24 hours.
- So we have to calculate energy by multiplying power by time.
- Hence, the correct answer is A, "12".
Question 34:
Which circuit provides a varying potential consistently?
Topic: Electrical Circuits
Correct Answer: C) Potential divider
- An adjustable voltage is produced by a potential divider, a simple circuit.
- It consists of a series of resistors, and the output voltage is taken from the junction between two resistors.
- The voltage can be varied by adjusting the values of the resistors.
- Hence, the correct answer is C, "Potential divider".
MCQs 35:
Which of Kirchhoff's rules states that a closed circuit has a zero algebraic sum of potential changes?
Topic: Electrical Circuit Rules
Correct Answer: B) Second rule
- Kirchhoff's second rule, also known as loop rule, states that the total of potential differences in any closed loop or mesh in a network must equal the sum of the emf's in that loop.
- Energy conservation is the essence of this rule.
MCQs 36:
Which law is demonstrated by a graph where the potential difference and current for a conductor are plotted, resulting in a straight line passing through the origin?
Topic: Electrical Conductivity and Laws
Correct Answer: C) Ohm's law
- If temperature and physical conditions remain constant, a conductor's current is directly proportional to its potential difference with its neighbor.
- If a graph of potential difference versus current is plotted, it produces a straight line passing through the origin, demonstrating this linear relationship.
Question 37:
What would be the resistance between any two corners if a wire of resistance “R” is bent into an equilateral triangle?
Topic: Resistance in Electrical Circuits
Correct Answer: B) 2/9 R
- If a wire of resistance R is bent into an equilateral triangle, each side of the triangle will have a resistance of R/3.
- Therefore, the resistance between any two corners of the triangle is calculated using parallel resistance formula.
- As a result, the correct answer is B, "2/9 R".
Question 38:
What does the graph of potential difference versus current illustrate, as per Ohm's law?
Topic: Ohm's Law and Electrical Graphs
Correct Answer: A) A straight line that originates from the axis intersection
- When the temperature remains constant, Ohm's law states that current and potential difference in a resistor are directly proportional.
- This linear relation reflects in a graph plotted between potential difference and current as a straight line emerging from the origin.
- Thus, the correct response is A, "A straight line that originates from the axis intersection".
Question 39:
In which direction does conventional current flow?
Topic: Basics of Electrical Current
Correct Answer: B) From the positive terminal towards the negative terminal
- Conventionally, the flow of current is considered from the positive terminal to the negative terminal.
- This flow is denoted as charge transported per unit time in a specific direction.
- Hence, the valid answer is B, "From the positive terminal towards the negative terminal".
Question 40:
For which material does resistance decrease when the temperature increases?
Topic: Temperature and Resistance in Materials
Correct Answer: C) Germanium
- In the case of semiconductors, the resistance decreases as temperature rises.
- Among the given options, Germanium is a semiconductor.
- Therefore, the correct answer is C, "Germanium".