intro
Question 1:
Under which circumstance does the electromotive force (e.m.f.) of a cell match its terminal voltage?
Topic: Electromotive Force and Terminal Voltage in Electrical Cells
Correct Answer: B) When no current is being drawn from the cell
- A cell's e.m.f. will be matched by the potential difference, or voltage, between its terminals.
- It occurs when the cell does not draw current, which means that its internal resistance is at zero potential drop.
- Therefore, the correct answer is B, "When no current is being drawn from the cell".
Question 2:
What would be the resistance of a coil at 0°C, given that its resistance is 4.2 ohms at 100°C and the temperature co-efficient of resistance of the coil material is 0.004/C?
Topic: Temperature Coefficient of Resistance
Correct Answer: A) 3 ohms
- The resistance of a coil at a different temperature can be calculated using the formula Rt = R0(1 + αT).
- In this scenario, the resistance at 0°C is the unknown to solve for.
- Substituting the given values into the formula and solving, the correct answer, A, "3 ohms", is obtained.
Question 3:
What is the unit of conductance?
Topic: Electrical Conductance
Correct Answer: D) All of these
- Conductance is the inverse of resistance and its units are the reciprocals of the units of resistance.
- Hence, the units of conductance can be seen as Mho, Siemen, or Ω-1.
- Therefore, the correct answer is D, "All of these".
Question 4:
If three bulbs with power ratings of 50W, 100W and 200W are connected in series to a 220V mains, which bulb will glow the most?
Topic: Power Rating and Brightness of Bulbs
Correct Answer: A) 50W bulb
- When bulbs of different power ratings are connected in series, the bulb with the least power rating tends to glow the brightest.
- This is because in a series connection, the current through each bulb is the same but the power dissipated differs.
- Thus, the correct answer is A, "50W bulb".
Question 5:
What is determined by the slope of a current-voltage (I-V) graph?
Topic: Interpretation of Current-Voltage (I-V) Graphs
Correct Answer: B) Conductance
- The slope of a current-voltage graph corresponds to a particular electrical property.
- This property is conductance, which is the reciprocal of resistance (1/R).
- Therefore, the correct answer is B, "Conductance".
Question 6:
Can you name an example of a non-ohmic resistance?
Topic: Ohm's Law and Non-ohmic Resistance
Correct Answer: A) Diode
- Certain materials or devices do not adhere to Ohm's law and are classified as non-ohmic.
- A diode is a common example of a non-ohmic device.
- Thus, the correct answer is A, "Diode".
Question 7:
Which of the following is considered a practical unit of power?
Topic: Units of Power
Correct Answer: C) Horse power (hp)
- Various units are used to measure power in different practical contexts.
- While watt is the standard SI unit of power, horsepower is commonly used in specific industries, such as automotive.
- Therefore, the correct answer is C, "Horse power (hp)".
Question 8:
When does a source with internal resistance 'r' deliver maximum power to a load resistance R?
Topic: Power Distribution in Circuits
Correct Answer: D) When R = r
- The principle of maximum power transfer states that a source delivers the highest power when the load's resistance equals the source's internal resistance.
- Hence, maximum power is transferred when R = r.
- Therefore, the correct answer is D, "When R = r".
Question 9:
What is the relative angle between a steady current and the electric field?
Topic: Current and Electric Field Direction
Correct Answer: A) 180 degrees
- The direction of a steady current is from the negative terminal to the positive terminal.
- Conversely, the electric field direction is from the positive terminal to the negative terminal.
- Thus, the angle between these two directions is 180 degrees, making the correct answer A, "180 degrees".
Question 10:
What principle does Kirchhoff's current rule uphold?
Topic: Kirchhoff's Current Law and Conservation Principles
Correct Answer: D) Conservation of Charge
- Using Kirchhoff's current law, the sum of currents entering and leaving a junction in an electrical circuit is equal.
- This law is a direct consequence of the conservation of electric charge.
- Hence, the correct answer is D, "Conservation of Charge".
Question 11:
Which of the following does not adhere to Ohm's Law?
Topic: Ohm's Law and Its Exceptions
Correct Answer: D) All of the specified
- The resistance between two points determines how much current passes through a conductor between them, whereas the voltage across the two points determines how much current passes.
- Some devices or materials, such as electrolytic solutions, gas discharge tubes, or vacuum tubes, do not follow this linear relationship and are known as non-linear or non-ohmic.
- Therefore, the correct answer is D, "All of the specified".
Question 12:
The reason for deviation in the I-V curve from a straight line is due to:
Topic: Characteristics of I-V Graphs
Correct Answer: B) Increasing temperature and resistance
- The current-voltage (I-V) relationship for a conductor is typically a straight line, as per Ohm's law.
- However, changes in temperature can affect the resistance of the material, thereby distorting the straight-line relationship.
- An increase in both temperature and resistance can cause this deviation, hence the correct answer is B, "Increasing temperature and resistance".
Question 9:
What is the relative angle between a steady current and the electric field?
Topic: Current and Electric Field Direction
Correct Answer: A) 180 degrees
- The direction of a steady current is from the negative terminal to the positive terminal.
- Conversely, the electric field direction is from the positive terminal to the negative terminal.
- Thus, the angle between these two directions is 180 degrees, making the correct answer A, "180 degrees".
Question 10:
What principle does Kirchhoff's current rule uphold?
Topic: Kirchhoff's Current Law and Conservation Principles
Correct Answer: D) Conservation of Charge
- Using Kirchhoff's current law, the sum of currents entering and leaving a junction in an electrical circuit is equal.
- This law is a direct consequence of the conservation of electric charge.
- Hence, the correct answer is D, "Conservation of Charge".
Question 11:
Which of the following does not adhere to Ohm's Law?
Topic: Ohm's Law and Its Exceptions
Correct Answer: D) All of the specified
- The resistance between two points determines how much current passes through a conductor between them, whereas the voltage across the two points determines how much current passes.
- Some devices or materials, such as electrolytic solutions, gas discharge tubes, or vacuum tubes, do not follow this linear relationship and are known as non-linear or non-ohmic.
- Therefore, the correct answer is D, "All of the specified".
Question 12:
The reason for deviation in the I-V curve from a straight line is due to:
Topic: Characteristics of I-V Graphs
Correct Answer: B) Increasing temperature and resistance
- The current-voltage (I-V) relationship for a conductor is typically a straight line, as per Ohm's law.
- However, changes in temperature can affect the resistance of the material, thereby distorting the straight-line relationship.
- An increase in both temperature and resistance can cause this deviation, hence the correct answer is B, "Increasing temperature and resistance".
Question 13:
The unit of the temperature coefficient of resistivity is:
Topic: Resistivity and Temperature Coefficient
Correct Answer: B) Per Kelvin (K-1)
- The temperature coefficient of resistivity, denoted by Alpha (α), quantifies the effect of temperature on the resistivity of a material.
- Its unit is inverse Kelvin (K-1), as it represents the change in resistivity per unit temperature change.
- Therefore, the correct answer is B, "Per Kelvin (K-1)".
Question 14:
To what type of current can Ohm's law be applied?
Topic: Application of Ohm's Law
Correct Answer: C) Both Alternating and Direct Current
- Ohm's Law establishes a linear relationship between current and voltage in a circuit.
- The voltage applied to a circuit determines the current flowing through it.
- This relationship holds true for both Direct Current (DC) and Alternating Current (AC), as long as mutual inductance in the circuit is accounted for.
- Therefore, the correct answer is C, "Both Alternating and Direct Current".
Question 15:
How is the Electromotive force (ε) related to the terminal potential (Vt)?
Topic: Relationship between EMF and Terminal Potential
Correct Answer: D) Both 'A' and 'B'
- The Electromotive force (EMF) of a circuit is the energy supplied per coulomb of charge, whereas the terminal potential is the potential difference across the terminals of the battery.
- Through the battery's internal resistance (r) and current (I), the EMF is related to the terminal potential.
- Both equations A and B correctly describe this relationship, hence the correct answer is D, "Both 'A' and 'B'".
Question 16:
What is the angular relationship between a stable current and the electric field?
Topic: Angular Relationship between Steady Current and Electric Field
Correct Answer: A) 180 degrees
- A steady current moves from the negative terminal to the positive terminal of a battery.
- Conversely, the electric field is directed from the positive terminal to the negative terminal.
- This results in an angular difference of 180 degrees between the two, meaning the correct answer is A, "180 degrees".
Question 17:
In what way is the Electromotive force (ε) connected to the terminal voltage (Vt)?
Topic: Interrelation between EMF and Terminal Voltage
Correct Answer: D) Yes, A and B are true
- The Electromotive force (or EMF) in a circuit is defined as the energy given for each coulomb of charge that passes through, whereas the terminal voltage represents the potential difference between them.
- These two quantities are tied to each other by the current (I) moving in the circuit and the inherent resistance (r) of the battery.
- This interrelation is aptly captured by both formulas A and B; thus, the correct answer is D, "Both A and B are correct".
Question 18:
Identify the correct graphical representation that exemplifies Ohm's Law:
Topic: Illustration of Ohm's Law
Explanation: A
- Ohm's Law demonstrates the direct proportionality between the current flowing in a conductor and the potential difference across it.
- This relationship, denoted as I ∝ V, is represented graphically by a straight line.
- Therefore, the accurate answer is A.
Question 19:
Which from the following does not exhibit a negative temperature coefficient?
Topic: Temperature Coefficient and Materials
Correct Answer: A. Aluminum
- Temperature coefficients of resistance measure how resistance varies with temperature.
- Aluminum has a positive temperature coefficient, which means the resistance increases with temperature.
- Therefore, the correct answer is A, "Aluminum".
Question 20:
What would be the equivalent resistance of a resistor with resistance "R" if it is divided into three equal segments and arranged in parallel?
Topic: Resistance Calculation of Segmented Resistors
Correct Answer: C) R/9
- When a resistor is divided into equal parts, the resistance of each segment is the total resistance divided by the number of segments.
- When resistors are arranged in parallel, the total resistance (Rt) is calculated using the formula: 1/Rt = 1/R1 + 1/R2 + 1/R3.
- In this case, since the three segments are identical, the formula simplifies to 1/Rt = 3/R. Solving for Rt gives R/9. Hence, the correct answer is C, "R/9".
MCQs 21:
What factor leads to an increase in a conductor's specific resistance?
Topic: Factors Influencing Specific Resistance
Correct Answer: A) Increase in temperature
- Specific resistance, or resistivity, is a material property that describes its opposition to the flow of electric current.
- It is largely independent of the dimensions of the conductor but can be affected by changes in temperature.
- As temperature increases, the vibration of atoms in the conductor increases, leading to an increase in resistivity. Hence, the correct answer is A, "Increase in temperature".
MCQs 22:
Under what condition will no current flow between two connected charged bodies?
Topic: Conditions for Current Flow
Correct Answer: B) They have the same potential
- Current flows from an area of high potential to an area of low potential.
- If two charged bodies are connected and they have the same potential, there will be no potential difference and hence no current flow.
- Therefore, the correct answer is B, "They have the same potential".
Question 23:
Given the resistance of a wire is 11 Ohm. If the length of this wire is extended by 10% due to stretching, what will the new resistance be?
Topic: Impact of Length on Resistance
Correct Answer: A) 11.2 ohm
- The resistance (R) of a wire directly varies with its length (L), as shown by the formula R = ρL/A, where ρ is the resistivity and A is the cross-sectional area.
- If the length is increased by 10%, the resistance increases by the same percentage.
- Therefore, the new resistance is 11 Ohm * 1.1 = 12.1 Ohm. Hence, the correct answer is A, "11.2 ohm".
Question 24:
In an ideal short circuit, how would you characterize the current?
Topic: Current in Short Circuits
Correct Answer: B) Infinity
- In an ideal short circuit, the resistance is essentially zero.
- According to Ohm's Law (I = V/R), if the resistance is zero, the current would theoretically be infinite.
- Thus, the correct answer is B, "Infinity".
Question 25:
A primary cell has an electromotive force of 2 volts. When it is short circuited, it produces a current of 4 amperes. What is the internal resistance in ohms of this cell?
Topic: Internal Resistance in Primary Cells
Correct Answer: A) 0.5
- The internal resistance (r) of a cell can be calculated using the formula r = E/I - R, where E is the electromotive force, I is the current, and R is the external resistance.
- In a short circuit, the external resistance (R) is zero. So, r = E/I = 2V/4A = 0.5 Ohm.
- Therefore, the correct answer is A, "0.5".
Question 26:
Who was the pioneering scientist that first discovered the D.C. Circuit?
Topic: Discovery of the D.C. Circuit
Correct Answer: C) Ohm
- The fundamental principle for analyzing DC electrical circuits, known as Ohm's Law, was first proposed by Georg Simon Ohm in 1826.
- Current flowing through two identical conductors determines the voltage difference between them.
Question 27:
In an electrolytic cell, what carries the current?
Topic: Current in Electrolytic Cells
Correct Answer: B) Both positive and negative ions
- In contrast to metallic conductors where electrons are the charge carriers, in electrolytes, both positive and negative ions serve as charge carriers.
- This is distinct from gases, where electrons and ions carry the charge, or semiconductors, where both electrons and holes are the charge carriers.
- As such, the correct answer is B, "Both positive and negative ions".
Question 28:
You have to shape a given mass of silver into a wire. Which combination of length (L) and cross-sectional area (A) will result in the smallest resistance?
Topic: Resistance in Relation to Length and Cross-Sectional Area
Correct Answer: D) L/2 and 2A
- Resistance of a wire varies directly with its length (L) and inversely with its cross-sectional area (A).
- This means that reducing the length of the wire and increasing its cross-sectional area will decrease the resistance.
- Therefore, the correct answer is D, "L/2 and 2A".