Page 105 - CITS - WCS - Mechanical

WORKSHOP SCIENCE - CITS

V ∝ I
or, V = I × R
Where:
V represents the voltage (in volts V)

I denotes the current (in amperes A)
R signifies the resistance (in ohms Ω).
Some common applications of Ohm’s Law:
In fuses

• To know the power consumption.
• To control the speed of fans.
• For deciding the size of resistors.
• To determine the voltage, resistance, or current of an electric circuit.
Example 1: If the resistance of an electric coil is 60 Ω and a current of 3.2 A flows through the resistance. Find
the voltage between two points.
Solution: According to the question, Resistance = 60 Ω
Current = 3.2 A

So in order to calculate the voltage we can use the formula, V = IR
V = I × R
V = 3.2 A × 60 Ω = 192 V

So the Voltage between the two points in the electric coil is 192 V.
Example 2: An EMF source of 10.0 V is connected to a purely resistive electrical appliance (a light bulb). An
electric current of 5.0 A flows through the bulb. Consider the conducting wires to be resistance-free. Calculate the
resistance of the appliance.
Solution: According to the question, the Voltage of the source = 10V
Current = 5.0 A

So in order to calculate the resistance we can use the formula, R= V/I
R = V/I
R = 10 V/5 A
R= 2Ω.
Series, Parallel and Series-Parallel Combination of Resistances

n a series combination, resistances are connected by an end to end such that the current flowing through all of
them is equal. Whereas in a parallel combination, is the resistances are connected in such a manner that they
get an equal voltage. In a series circuit, the same amount of current flows through all the components placed in
it. On the other hand, in parallel circuits, the components are placed in parallel with each other due to which the
circuit splits the current flow.
Concept, Definitions and Units of Electrical Work, Power and Energy With Related Problems
Electrical work is equal to the amount of charge multiplied by the voltage difference. It describes the effort put in
to move a charge between two points. This principle is embodied in the formula W=QV, where W represents work,
Q charge, and V voltage.
Electric power is the rate at which work is done or energy is transferred in an electrical circuit. Simply put, it is a
measure of how much energy is used in a span of time. SI unit of power is the watt (W), which is equal to one
joule per second. Electric energy is generated from potential differences in a circuit, causing current to flow. The
SI unit of energy is joule.

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CITS : WCS - Mechanical - Exercise 9