FYUG Even Semester Exam, 2025 Electrical Circuits and Safety
UNIT-I
Question 1 (a) 1 Mark
State Ohm's law.
Ohm's law states that the current flowing through a conductor between two points is directly proportional to the voltage across the two points, provided physical conditions like temperature remain constant.
Question 1 (b) 1 Mark
Define one-ampere electric current.
One ampere is defined as the flow of one coulomb of electric charge per second through a cross-section of a conductor.
Question 1 (c) 1 Mark
What do you mean by electrical load?
An electrical load is a component or portion of a circuit that consumes electric power, such as appliances, lights, or machines.
Question 1 (d) 1 Mark
What is the average value of an alternating current in one complete cycle?
In a complete cycle, the positive half and negative half cancel each other out.
Question 2 (b) 5 Marks
Explain Kirchhoff's current law (KCL).
Kirchhoff's Current Law (KCL) states that the total current entering a junction or node is exactly equal to the total current leaving that node. This is based on the Law of Conservation of Charge.
Question 3 (a) 5 Marks
For the given circuit, find the value of total resistance and value of branch currents I1, I2 and I3.
Circuit Data: Voltage (V) = 6V. Series resistor = 0.2 ohm. Parallel resistors: R1 = 2 ohm, R2 = 3 ohm, R3 = 6 ohm.
- Parallel Resistance (Rp):
1/Rp = 1/2 + 1/3 + 1/6 = (3 + 2 + 1)/6 = 6/6 = 1.
So, Rp = 1 ohm. - Total Resistance (Rt):
Rt = Series resistor + Rp = 0.2 + 1 = 1.2 ohm. - Total Current (It):
It = V / Rt = 6 / 1.2 = 5 A. - Branch Currents: Since the voltage across the parallel group is Vp = It * Rp = 5 * 1 = 5V:
I1 = 5V / 2 ohm = 2.5 A
I2 = 5V / 3 ohm = 1.67 A
I3 = 5V / 6 ohm = 0.83 A
Question 3 (b) 5 Marks
State differences between a.c. and d.c. If a sinusoidal signal has maximum value 200 mV, find r.m.s. value.
| Feature | A.C. Electricity | D.C. Electricity |
|---|---|---|
| Direction | Changes periodically | Remains constant |
| Source | Alternators, AC Mains | Batteries, Solar Cells |
Numerical: Given V_max = 200 mV.
UNIT-II
Question 4 (b) 1 Mark
What is the purpose of a ceiling rose?
A ceiling rose is used to provide a connection point for pendant light fittings or fans to the fixed wiring of a building.
Question 6 (a) 5 Marks
Explain conduit wiring and concealed wiring. Mention one advantage.
- Conduit Wiring: Wires are drawn through metal or PVC tubes (conduits) installed on walls.
- Concealed Wiring: Conduits are buried inside the wall plaster for a neat appearance.
Advantage: It provides high protection against mechanical damage and fire.
UNIT-III
Question 7 (b) 1 Mark
Define power factor.
Power factor is the ratio of the real power (kW) to the apparent power (kVA) in an electrical circuit.
Question 8 (a) 5 Marks
What is the principle of transformer?
A transformer works on the principle of Faraday's Law of Mutual Induction. When an alternating current flows through the primary coil, it creates a changing magnetic flux, which induces an e.m.f. in the secondary coil.
UNIT-IV
Question 12 (b) 5 Marks
Explain the working of a full-wave rectifier with necessary circuit diagram.
A full-wave rectifier converts both halves of the AC cycle into pulsating DC. It typically uses two diodes with a center-tapped transformer or four diodes in a bridge configuration.
UNIT-V
Question 13 (a) 1 Mark
What are the three types of electrical hazards?
The three main types are electrical shock, burns, and fires (including explosions).
Question 15 (a) 5 Marks
What does the term overloading mean and how can it be prevented?
Overloading: This occurs when too many electrical appliances are connected to a single socket or circuit, drawing current beyond its rated capacity.
Prevention:
- Avoid using multi-plug adapters for high-power devices.
- Use Circuit Breakers (MCBs) or fuses of appropriate ratings.
- Regularly inspect the electrical load distribution.