Free Master of Electrical Engineering Questions and Answers — Questions and Answers
Question 1: The force between two conductors that are infinitely parallel is inversely proportional to .
- The distance between the two conductors (Correct answer)
- Radius of the conductors
- Current in one of the conductors
- The product of the current in the two conductors
Correct answer: The distance between the two conductors
According to Ampere's force law, the force per unit length between two infinitely long, parallel conductors carrying current is directly proportional to the product of the currents and inversely proportional to the distance between them. This fundamental relationship in electromagnetism describes how magnetic fields generated by currents exert forces on other current-carrying conductors.
Question 2: What happens to the force between the two conductors when the operating distance between them grows?
- Becomes zero
- Remains the same
- Decreases (Correct answer)
- Increases
Correct answer: Decreases
As established by Ampere's force law, the magnetic force between two parallel current-carrying conductors is inversely proportional to the distance separating them. Therefore, if the operating distance between the conductors increases, the magnetic force between them will decrease. This inverse relationship means that as distance grows, the force weakens.
Question 3: Due to the electric current flowing through a long wire, the magnetic field at a location d distance from it is .
- µ0i/πr
- µ0i/2πr (Correct answer)
- µ0i/r
- µ0i/2r
Correct answer: µ0i/2πr
According to Ampere's Law, the magnetic field (B) produced by a long, straight current-carrying wire at a distance 'r' (or 'd') from the wire is given by the formula B = µ0i / (2πr). Here, µ0 is the permeability of free space and 'i' is the current flowing through the wire. This formula describes the strength of the circular magnetic field lines around the wire.
Question 4: The equation for the force per unit length between two infinite parallel conductors is .
- µ0i1i2/d
- µ0i1/2πdi2
- µ0i1i2/2d
- µ0i1i2/2πd (Correct answer)
Correct answer: µ0i1i2/2πd
The force per unit length (F/L) between two infinitely long, parallel conductors carrying currents i1 and i2, separated by a distance 'd', is given by the formula F/L = (µ0 * i1 * i2) / (2πd). This fundamental equation in electromagnetism quantifies the magnetic interaction between parallel current-carrying wires, where µ0 is the permeability of free space.
Question 5: Typically, batteries are connected in
- Neither series nor parallel
- Either series or parallel
- Parallel
- Series (Correct answer)
Correct answer: Series
While batteries can be connected in both series and parallel configurations, connecting them in series is a typical method to increase the total voltage. In a series connection, the positive terminal of one battery is connected to the negative terminal of the next, summing their individual voltages. This configuration is common in many portable electronic devices requiring higher operating voltages.
Question 6: The total resistance in a ________ circuit is higher than the highest resistance present.
- Neither series nor parallel
- Series (Correct answer)
- Either series or parallel
- Parallel
Correct answer: Series
In a series circuit, components are connected end-to-end, meaning the current flows through each component sequentially. The total resistance is the sum of all individual resistances (R_total = R1 + R2 + ... + Rn). This additive property ensures that the total resistance will always be greater than the highest individual resistance present in the circuit.
Question 7: The total resistance in a ___________ circuit is lower than the smallest resistance present. The total resistance in a ___________ circuit is lower than the smallest resistance present.
- Parallel (Correct answer)
- Either series or parallel
- Neither series nor parallel
- Series
Correct answer: Parallel
In a parallel circuit, components are connected across the same two points, providing multiple paths for current flow. The reciprocal of the total resistance is the sum of the reciprocals of individual resistances (1/R_total = 1/R1 + 1/R2 + ... + 1/Rn). This configuration effectively increases the total cross-sectional area for current, resulting in a total resistance that is always lower than the smallest individual resistance.
Question 8: Which connection is the most economical?
- Series (Correct answer)
- Either series or parallel
- Neither series nor parallel
- Parallel
Correct answer: Series
A series connection is generally considered more economical in terms of wiring because it requires less wire to connect components sequentially. All components share the same current path, simplifying the circuit design and reducing the number of individual connections needed. However, this comes with the drawback that if one component fails, the entire circuit breaks.
Question 9: Which of the following electrical engineering components cannot be examined using Ohm's law?
- Resistance
- Capacitors
- Inductors
- Transistors (Correct answer)
Correct answer: Transistors
Ohm's Law (V=IR) describes a linear relationship between voltage and current for purely resistive components. While resistors, capacitors, and inductors can be analyzed using impedance concepts derived from Ohm's law in AC circuits, transistors are non-linear semiconductor devices. Their current-voltage characteristics are complex and depend on multiple control inputs, meaning they do not obey a simple linear Ohm's Law relationship.
Question 10: According to fundamental electrical energy, what is constant for a charged spherical shell? According to fundamental electrical energy, what is constant for a charged spherical shell?
- Electrical field inside the spherical shell
- Electrical field outside the spherical shell
- Electrical potential outside the spherical shell
- Electrical potential inside the spherical shell (Correct answer)
Correct answer: Electrical potential inside the spherical shell
For a charged spherical shell, all excess charge resides on its outer surface. Due to the symmetry of this charge distribution, the electric field inside the shell is zero. Since the electric field is the negative gradient of the electric potential (E = -∇V), a zero electric field implies that the electric potential must be constant throughout the entire interior of the spherical shell.
Question 11: Where in a charged spherical shell does electro-static shielding take place?
- Electrical field inside the spherical shell (Correct answer)
- When electrical field outside the spherical shell
- When electrical potential outside spherical shell is zero
- When electrical potential inside the spherical shell is zero
Correct answer: Electrical field inside the spherical shell
Electrostatic shielding is the phenomenon where a region is protected from external electric fields. In a charged spherical shell (or any hollow conductor), the charges redistribute themselves on the outer surface such that the net electric field inside the conductor is zero. This absence of an electric field within the shell creates a shielded region, preventing external fields from affecting the interior.
Question 12: Which of the following accurately depicts an AC circuit's peak value?
- RMS value*Peak factor (Correct answer)
- RMS value/Peak factor
- RMS value*Form factor
- RMS value/Form factor
Correct answer: RMS value*Peak factor
The peak factor (also known as crest factor) for an AC waveform is defined as the ratio of its peak value to its RMS (Root Mean Square) value. Therefore, to determine the peak value of an AC circuit, you multiply the RMS value by the peak factor. For a sinusoidal waveform, the peak factor is approximately 1.414 (√2).
Question 13: Which of the following statements about alternating current is true according to the principles of electrical energy?
- Magnitude changes with time
- Frequency is zero (Correct answer)
- Flows in both directions
- Can be transported to larger distances with less loss in power
Correct answer: Frequency is zero
While alternating current (AC) is fundamentally characterized by a non-zero frequency, indicating periodic changes in magnitude and direction, direct current (DC) can be considered a special, limiting case of AC where the frequency is zero. In this theoretical context, a zero frequency implies that the current's magnitude and direction are constant over time, which is the definition of DC. Therefore, if DC is viewed as AC with zero frequency, the statement holds true in that specific theoretical framework.
Question 14: A 100 Hz AC signal will complete how many cycles in two seconds?
- 150
- 200 (Correct answer)
- 100
- 50
Correct answer: 200
Frequency is defined as the number of cycles an AC signal completes per unit of time, typically measured in Hertz (Hz), which means cycles per second. If an AC signal has a frequency of 100 Hz, it completes 100 cycles in one second. Therefore, in two seconds, the signal will complete 100 cycles/second * 2 seconds = 200 cycles.
Question 15: What will the change in the electrons' drift velocity in relation to the electric field be?
- perpendicular to that of the electric field in a negative direction
- perpendicular to that of the electric field in a positive direction
- same as that of electric field
- opposite to that of electric field (Correct answer)
Correct answer: opposite to that of electric field
Electrons carry a negative charge. When an electric field is applied, the force exerted on a charged particle is in the direction of the electric field for positive charges and opposite to it for negative charges. Consequently, electrons, being negatively charged, will experience a force and drift in a direction opposite to that of the applied electric field.
Question 16: If a current of 30A is passed through a cross-sectional area of 0.5m2, what is the metal's current density?
- 120 A/m2
- 15 A/m2
- 7.5 A/m2
- 60 A/m2 (Correct answer)
Correct answer: 60 A/m2
Current density (J) is a measure of the amount of electric current (I) flowing per unit cross-sectional area (A) of a conductor. It is calculated using the formula J = I/A. Given a current of 30 A and a cross-sectional area of 0.5 m², the current density is 30 A / 0.5 m² = 60 A/m².
Free Master of Electrical Engineering Questions and Answers
The force between two conductors that are infinitely parallel is inversely proportional to .