Current Electricity is an important topic from JEE Main / JEE Advanced Exam Point of view. Every year there are 1-3 questions asked from this topic. This short notes on Current Electricity will help you in revising the topic before the JEE Main & IIT JEE Advanced Exam. This is the second part of our current electricity study notes.
Resistor and their combination
Carbon Resistors Carbon resistors are comparatively small inexpensive therefore it has widespread use in electronic circuits. Carbon resistors are small in size and hence their standards are given using a colour code.
Colour Codes for Carbon Resistors
Combination of resistors:
Series Combination:
Parallel Combination:
Temperature dependence of resistance:
The resistance of a conductor has a linear dependency on the temperature as
where is the temperature coefficient.
Cell and their Combination
Potential difference and potential of Cell
A cell has two electrodes one positive (P) and one negative (N). Both are immersed in an electrolytic solution. In the solution, the electrodes interchange charges with the electrolyte. The positive electrode has a potential difference between itself and the electrolyte solution similarly, the negative electrode develops a negative potential (V– (V– ≥0) relative to the electrolyte. When there is no current, the electrolyte has the same potential throughout, so that the potential difference between the electrodes is known as the Emf of the battery.
Emf is the potential difference between the positive and negative electrodes when no current is flowing through the cell an open circuit,
This difference is called the electromotive force (Emf) of the cell and is denoted by ε.
If the circuit is closed then,
Here, r is the internal resistance of the cell.
The internal resistance of the cell is the resistance offered by the electrolyte inside the cell.
The maximum current flowing in the circuit is:
Combination of cells in series:
If n numbers of cells are connected in series
Combination of cells in parallel
If n numbers of cells are connected in parallel
Kirchhoff's Law
1. Junction rule: At any junction, the sum of the currents entering the junction is equal to the sum of currents leaving the junction.
2. Loop rule: The algebraic sum of changes in potential around any closed loop involving resistors and cells in the loop is zero.
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