Important Formulas and Equations for Electrical Engineering Optional Subject Exam

1. 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. It can be represented by the equation:
V = I * R
Where,
V is the voltage,
I is the current, and
R is the resistance.

2. Power Formula:
The power formula relates power, voltage, and current. It can be expressed as:
P = V * I
Where,
P is the power,
V is the voltage, and
I is the current.

3. Kirchhoff's Laws:
Kirchhoff's Laws are fundamental laws used to analyze electrical circuits. They include:
- Kirchhoff's Current Law (KCL): The sum of currents entering a node is equal to the sum of currents leaving the node.
- Kirchhoff's Voltage Law (KVL): The sum of voltage drops around any closed loop in a circuit is equal to zero.

4. Maximum Power Transfer Theorem:
The Maximum Power Transfer Theorem states that the maximum power is transferred from a source to a load when the resistance of the load is equal to the internal resistance of the source. Mathematically, it can be written as:
RL = RS
Where,
RL is the load resistance, and
RS is the source resistance.

5. Transformer Equations:
Transformers are essential devices in electrical power systems. The key equations related to transformers include:
- Turns Ratio: The ratio of the number of turns in the primary and secondary windings determines the voltage transformation. It can be expressed as:
Np/Ns = Vp/Vs
Where,
Np and Ns are the number of turns in the primary and secondary windings, respectively, and
Vp and Vs are the primary and secondary voltages, respectively.

- Transformer Power Equation: The power in a transformer can be calculated using the equation:
P = Vp * Ip = Vs * Is
Where,
P is the power,
Vp and Vs are the primary and secondary voltages, respectively, and
Ip and Is are the primary and secondary currents, respectively.

6. Biot-Savart Law:
The Biot-Savart Law is used to calculate the magnetic field produced by a current-carrying wire. It can be given as:
B = (μ0 * I * dl x r) / (4π * r^2)
Where,
B is the magnetic field,
μ0 is the permeability of free space,
I is the current,
dl is the length element of the wire,
r is the distance from the wire, and
π is a mathematical constant.

These are some of the important formulas and equations to remember for the Electrical Engineering optional subject exam. Understanding and applying these equations can greatly assist in solving problems related to electrical circuits, power systems, and electromagnetism.