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What does the Current Electricity revision sheet cover?

junction, loop, branch, Junction, loop, branch, kirchhoff's first law, junction law, Kirchhoff's first law: current law (junction law), algebraic sum of currents at a junction is zero, sign convention, kirchhoff's second law, loop law, voltage law.

Is this for Class 12 Maharashtra HSC Physics?

Yes, it is written for the Maharashtra HSC Physics syllabus.

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Current Electricity — Class 12 Maharashtra HSC Physics revision notes

A 7-page visual revision sheet for Current Electricity, written for Class 12 Maharashtra HSC Physics. Formulas, diagrams and the traps that cost marks, laid out to be read the night before rather than the term before. Free, and it opens inside CapCompass.

Current Electricity revision notes, page 1 of 7 — Page 1 of 7. The remaining 6 pages open in the app.

Current Electricity in one look

Kirchhoff's laws, the bridges built on them, and the null-deflection potentiometer

Junction, loop, branch

junction: point where two or more conductors meet
loop: any closed conducting path in a network, also called a mesh
branch: part of the network lying between two junctions
a network too complex for series/parallel rules needs Kirchhoff's two laws

Kirchhoff's first law: current law (junction law)

algebraic sum of currents at a junction is zero Σ_i=1^nI_i=0
sign convention current arriving=+, current leaving=-

Kirchhoff's second law: voltage law (loop law)

sum of IR drops and emfs around any closed loop is zero Σ IR+Σε=0

Steps for solving a network

choose a direction for every unknown current, label it
reduce variables using the junction law at each meeting point
identify the independent loops in the network
apply the voltage law to each independent loop
solve the resulting equations simultaneously
a negative current just flows opposite to the chosen direction

Page 1 of 7. The full sheet, all 7 pages, opens free in the app.

What this Current Electricity sheet covers

junction
loop
branch
Junction, loop, branch
kirchhoff's first law
junction law
Kirchhoff's first law: current law (junction law)
algebraic sum of currents at a junction is zero
sign convention
kirchhoff's second law
loop law
voltage law
Kirchhoff's second law: voltage law (loop law)
sum of IR drops and emfs around any closed loop is zero
Steps for solving a network
wheatstone bridge
The Wheatstone bridge
balanced wheatstone bridge
balance condition
loop ABDA with I_g=0
loop BCDB with I_g=0
dividing the two, the balance condition
Applications of the bridge
metre bridge
The metre bridge
metre bridge balance
unknown resistance metre bridge
balance condition, l_x and l_R the two wire lengths
unknown resistance
specific resistance of the unknown wire X, radius r, length L
post office box
The post office box
Metre bridge vs post office box
potentiometer
Potentiometer, the principle
comparing emf
sum and difference method
Comparing the emf of two cells
null lengths l_1 and l_2 correspond to emf epsilon_1 and epsilon_2
so the emfs compare directly as lengths
sum and difference method, componendo-dividendo
internal resistance
internal resistance of a cell
open circuit, null length l_1 corresponds to emf epsilon
closed through a known resistance R, null length l_2 corresponds to terminal voltage V
voltage divider
Potentiometer as a voltage divider
galvanometer to ammeter
shunt resistance
Galvanometer to ammeter: the shunt
shunt S in parallel carries the rest of the current, GI_g=S(I-I_g)
to extend the range n times, I=nI_g
fraction of the total current through the shunt
galvanometer to voltmeter
series resistance voltmeter
Galvanometer to voltmeter: the series resistor
resistance X in series drops the remaining voltage, V=I_g(G+X)
to extend the range n_V times
Symbols
Charging and discharging a capacitor
Endless ladders and symmetric networks
Traps that cost marks
Tricks that save time

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