Definitions [2]
Define potential gradient of the potentiometer wire.
The potential gradient of a potentiometer wire is defined as the change in electric potential (voltage) per unit length of the wire.
Mathematically,
Potential Gradient = `V/L`
Define a Potentiometer.
A potentiometer is a manually adjustable, variable resistor with three terminals. Two terminals are connected to the ends of a resistive element, and the third terminal is connected to an adjustable wiper. The position of the wiper sets the resistive divider ratio.
Theorems and Laws [1]
Obtain the balancing condition for the Wheatstone bridge arrangements as shown in Figure 4 below:
Let `I_3` and `I_4` be the currents in resistors Q and S respectively . Let `I_g` be the current through galvanometer. For balanced condition,
`I_g = 0`
Applying junction law at ‘b’ we get
`I_1 = I_3 + I_g`
`because I_g = 0 , I_1 = I_3` ....(i)
Applying junction law at ‘d’, we get
`I_2 + I_g = I_4`
`because I_g = 0 , I_2 = I_4` ....(ii)
Applying loop law in the loop abda, we get
`-I_1·P - I_g·Q + -I_2·R = 0`
⇒ `-I_1P + I_2R = 0` (`because I_g = 0`)
⇒ `I_1P = I_2R`
⇒ `P/R = I_2/I_1` ....(iii)
Applying loop law in the loop bcdb, we get
`-I_3·Q + I_4·S + I_g·6 = 0`
⇒ `-I_3·Q + I_4·S + 0 = 0 (because I_g =0)`
⇒ `-I_3Q = I_4S`
⇒ `Q/S = I_4/I_3`
⇒ `Q/S = I_2/I_1` ...(iv) [using eq.(i) and (ii)]
From eq. (iii) and (iv), `P/ R = Q/s`
⇒ `P/Q = R/S`
This is the balanced condition.
Important Questions [26]
- What is is Equivalent to Kirchhoff'S Junction Law
- Obtain the condition for bridge balance in Wheatstone’s bridge.
- Kirchhoff'S Voltage Law and Current Law Are Respectively in Accordance with the Conservation of
- Explain with a Neat Circuit Diagram How Will You Determine Unknown Resistance ‘X' by Using Meter Bridge
- Four Resistances 4ω,8ω,Xω, and 6ω Are Connected in a Series So as to Form Wheatstone’S Network. If the Network is Balanced, Find the Value of ‘X
- State any two sources of errors in the meter-bridge experiment. Explain how they can be minimized.
- A Potentiometer Wire Has Length of 2m and Resistance 10ω. It is Connected in Series with Resistance 990ω and a Cell of E.M.F. 2v. Calculate the Potential Gradient Along the Wire.
- When unknown resistance is determined by meter bridge, the error due to contact resistance is minimized ______.
- The Resistance of 11 is Connected in Right Gap. If Null Point is Obtained at a Distance of 45 Cm from the Left End, Find the Resistance of Metal Ring.
- Explain the Principle of Potentiometer.
- An Unknown Resistance is Placed in the Left Gap and Resistance of 50 Ohm is Placed in the Right Gap of a Meter Bridge. the Null Point is Obtained at 40 Cm from the Left End. Determine the Unknown Resistance.
- What is the Balancing Length for Its Terminal Potential Difference When Shunted with Resistance R
- The instrument which can measure terminal potential difference as well as electromotive force (e.m. f.) is ______ Wheatstone’s meter bridge Voltmeter Potentiometer Galvanometer
- State Any ‘Two’ Possible Sources of Errors in Meter-bridge Experiment
- A Potentiometer Wire Has a Length of 4 m and a Resistance of 5Ω . What Resistance Should Be Connected in Series with a Potentiometer Wire and a Cell of E.M.F. 2 V Having Internal Resistance 1 ω to Get a Potential Gradient of 10-3 V/cm
- Calculate the Balancing Length When the Cell is in Open Circuit.
- When a Resistance of 12 Ohm is Connected Across a Cell, Its Terminal Potential Difference Is Balanced by 120 Cm Length of Potentiometer Wire.
- Si Unit of Potential Gradient is _______.
- State the advantages of potentiometer over voltmeter.
- When a Resistor of 5ω is Connected Across the Cell, Its Terminal Potential Difference is Balanced by 150 Cm of Potentiometer Wire and When a Resistance of 10 ω is Connected Across the Cell
- Define potential gradient of the potentiometer wire.
- Accuracy of potentiometer can be easily increased by ______.
- Distinguish between a potentiometer and a voltmeter.
- Describe with the help of a neat circuit diagram how you will determine the internal resistance of a cell by using a potentiometer. Derive the necessary formula.
- A potentionmeter wire has resistance of per unit length of 0.1 Ω/m. A cell of e.m.f. 1.5 V balances against 300 cm length of the wire. Find the current in the potentiometer wire.
- What is the value of resistance for an ideal voltmeter?
