Wheatstone Bridge Flashcards
(15 cards)
What is Wheat stone bridge?
The Wheatstone Bridge is an electrical circuit used to measure an unknown resistance by comparing it with known resistances.
Construction: Types of resistors
It consist of 4 resistors P and Q which are known value, variable resistance R and resistor X which we have to find.
Construction: Battery and Galvanometer
Battery is connected b/w junctions A and C. Galvanometer is connected b/w B and D.
Working: Key switched ON
The value of P and Q are properly fixed. When the key is switched on, the current I divides unequally between two branches and the galvanometer shows current.
Working: Adjust R
Then we adjust R (the variable resistance) until the galvanometer shows no deflection.This means the potential on both sides of the galvanometer is equal, so no current flows through it.
What is a null point?
When the potential on both sides of the galvanometer is equal, so no current flows through it.
Working: Naming Currents I1 and I2
Let I1 and I2 be the currents through P and R respectively when the bridge is balanced.
The current in Q and X are also I1 and I2 respectively.
Working: Voltage drop
As the galvanometer reads 0, points B and D are at the same potential. This means that voltage drops from A to B and A to D must be equal. Also voltage drop from B to C and D to C must be equal.
State Ohm’s LAW
The current (I) flowing through a conductor is directly proportional to the voltage (V) across it, provided the temperature and other physical conditions remain constant.
Formula: V=I×R
What is Rheostat? Explain its working.
A rheostat is a variable resistor a device used to control current in a circuit by changing resistance.
If the sliding contact is shifted away from the terminal A, the length and hence the resistance increases. If the sliding contact is moved towards A, the resistance decreases.
What is a Potential divider?
A potential divider is a circuit that divides the input voltage into smaller output voltages using resistors connected in series.
When two resistors are connected in series:
The same current flows through both.
The voltage divides in proportion to the resistance.
So the resistor with the larger value gets more voltage.
What is a Transistor?
A transistor is a three-terminal electronic device that can control the flow of current or amplify signals by acting as a switch or amplifier.
Explain transistor types?
Negative temperature coefficient thermistor (NTC): R is inversly propotional to T.
Positive temperature coefficient thermistor (PTC): R is directly propotional to T.
What is EMF?
Electromotive force (EMF) is the total energy supplied by a source (such as a cell or battery) per coulomb of charge.
It is measured in volts (V).
Formula: E=W/Q
What is Electric power?
Electric power is the rate at which electrical energy is transferred or used in a circuit.
In simple words: It tells how fast electricity is being used or produced by a device like a bulb, fan, or battery.
P=VI
