METRE BRIDGE Flashcards
to find resistance of wire . To verify law of combination of series resistance .
- Why the metre Bridge is called so?
The M.B uses a wire of one metre length.
- M.B. is also known as _______?
Slide wire Bridge
- Give the working principle of M.B?
Balanced Wheatstone Bridge equation, P/Q = R/S
- Which materials are used as M.B wire?
Constantine, Manganine
- What are the requirements of M.B wire?
High resistivity, Uniform resistance, inextensible & low alpha (temp coefficient) value .
- Can we use copper wire as M.B wire?
No, Copper has low resistance
- Name the instruments works under balanced wheat stone’s Bridge principle?
Metre Bridge & Post Office Box (also used to find unknown resistance value)
- What is meant by null point of M.B?
It is a point on M.B wire, when the Jo – key is kept on that point – Galvanometer shows null deflection.
- Name the method under which this experiment works?
Null deflection method.
- Why do we prefer the null point of a M.B in the middle of the bridge wire?
If the null point is in the middle, the ratio of two arms ( and 100 – ) are equal and the end resistance will not be affected.
- Is it necessary that the Bridge wire should have uniform area of cross section? Why?
Yes, because while deriving the formula P/Q = R/S, the resistance is proportional to length ( P ∝
and Q ∝ 100 – ). To take Resistance is proportional to length; we should keep area of cross section
as constant.
- When do we say the M.B is balanced?
When the ratio of resistances in the arms of M.B are equal as
P/Q = R/S, the M.B is said to be balanced.
- Why do we interchange the known resistance (Resistance box) and unknown resistance (resistance
wire) in the left gap and right gap and repeat the experiment?
It is for nullifying the end correction.
- What is the use of high resistance in the circuit?
It protects galvanometer from high current.
- Which method is more prefer to measure the unknown resistance – M.M or ohm’s law method?
Metre Bridge experiment – because it works under null deflection. But the current drop will occur
through voltmeter in Ohm’s law experiment.
