Electrical Circuits Flashcards
KCL and KVL.
KCL is also known as junction law which states that the algebraic sum of all the current flowing towards the junction is zero.
KVL also known as voltage law or loop law states that the algebraic sum of emf is equal to the algebraic sum of potential drop.
Wheat stone bridge principle.Prove
When the bridge is balanced the product of resistance of the opposite arms of the circut are equal.
P/Q=X/R
To prove this we have to apply krichoffs law.
I=I1+I2
-I1P+IgG+I2X=0
-{I1-Ig}Q+IgG+I2R=0
WHEN Ig=0 we get,
I1P=I2X and I1Q=I2R
dividing we get,
P/Q=X/R
Principle of potentiometer and its prove.
current passes through a long wire having uniform cross section area, the potential drop across any portion of the wire is equal to the length of that portion of the wire.
To prove we need to know the E and V
E is directly propotional to l1 where as V is directly propotional to l2 divide the both equation then put the value of E and V E=Ir whereas V=IR.
used to fine internal resistance of a cell.
Meter bridge, components of it and their formula.
Meter bridge works on the principle of wheat stone which is used to determine the unknown resistance of the cell.
Made up of alloy, magnanin and wire of uniform cross section area.
Formula is determined by the wheatstone bridge.
P/Q=X/R=[100-l]/l
X=R[100-l]/l
Shunt and its use to convert galvanometer into ammeter.
Shunt is the electrical device which is used to pass out the excess current and helps to convert galvanometer into ammeter.
To convert galvanometer into ammeter first we need to write 1/R=1/G+1/S
then we get the value of R which is GS/G+S in this the value of S is very small so R is also very small. then we apply the formula of V which is IR.
Then current passing through G is V/G and current passing through S is V/S then pd across S= pd acress G
then we get {I-Ig}S=IgG
Then find the value of S.
Convert the galvanometer into voltmeter.
by adding a high resistance.
V=Ig(G+R) and find the value of R.
Why is potentiometer preferred to measure the emf rather than voltmeter?
potentiometer works on the null deflection method whereas voltmeter works on the deflection method so potentiometer measures more accurately.
Potential gradient
potential difference per unit length of the wire.
Potential gradient=IAρ.
