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प्रश्न
Distinguish between a potentiometer and a voltmeter.
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उत्तर १
| Potentiometer | Voltmeter | |
| 1. | The emf of a cell, potential difference, and internal resistance are all measured with a potentiometer. | A voltmeter can be used to determine a cell's potential difference and terminal voltage. However, it cannot be used to measure the emf of a cell. |
| 2. | It has a high level of accuracy and sensitivity. | Its accuracy and sensitivity are less as compared to a potentiometer. |
| 3. | It is not a portable instrument. | It is a portable instrument. |
| 4. | It does not give a direct reading. | It gives a direct reading. |
उत्तर २
| No. | Potentiometer | Voltmeter |
| i. | Its resistance is infinite. | Its resistance is high but finite. |
| ii. | It does not draw any current from the source of known e.m.f. | It draws some current from the source of e.m.f. |
| iii. | The potential difference measured by it is equal to the actual potential difference (p.d.). | The potential difference measured by it is less than the actual potential difference (p.d.). |
| iv. | It has high sensitivity. | It has low sensitivity. |
| v. | It measures e.m.f as well as p.d. | It measures only p.d. |
| vi. | It is used to measure the internal resistance of a cell. | It cannot be used to measure the internal resistance of a cell. |
| vii. | It is more accurate. | It is less accurate. |
| viii. | It does not give a direct reading. | It gives a direct reading. |
| ix. | It is not portable. | It is portable. |
| x. | It is used to measure lower voltage values only. | It is used to measure lower as well as higher voltage values. |
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संबंधित प्रश्न
A potentiometer wire has resistance of per unit length of 0.1 Ω/m. A cell of e.m.f. 1.5 V balances against a 300 cm length of the wire. Find the current in the potentiometer wire.
State the principle of working of a potentiometer.
On what factors does the potential gradient of the wire depend?
State the advantages of potentiometer over voltmeter.
SI unit of potential gradient is _______.
(a) V cm
(b) `V/"cm"`
(c) Vm
(d) `V/m`
In the given circuit, with steady current, calculate the potential drop across the capacitor and the charge stored in it.
State the underlying principle of a potentiometer ?
In the given circuit in the steady state, obtain the expressions for (a) the potential drop (b) the charge and (c) the energy stored in the capacitor, C.
Describe briefly, with the help of a circuit diagram, how a potentiometer is used to determine the internal resistance of a cell.
Write the principle of working of a potentiometer. Describe briefly, with the help of a circuit diagram, how a potentiometer is used to determine the internal resistance of a given cell.
The net resistance of a voltmeter should be large to ensure that ______________ .
A student uses the circuit diagram of a potentiometer as shown in the figure
(a) for a steady current I passing through the potentiometer wire, he gets a null point for the cell ε1. and not for ε2. Give the reason for this observation and suggest how this difficulty can be resolved.
(b) What is the function of resistance R used in the circuit? How will the change in its value affect the null point?
(c) How can the sensitivity of the potentiometer be increased?
When the balance point is obtained in the potentiometer, a current is drawn from ______.
Define potential gradient of the potentiometer wire.
How is potential gradient measured? Explain.
A potentiometer wire has a length of 1.5 m and a resistance of 10 Ω. It is connected in series with the cell of emf 4 Volt and internal resistance 5 Ω. Calculate the potential drop per centimeter of the wire.
Why is a potentiometer preferred over a voltmeter for measuring emf?
The emf of a cell is balanced by a length of 120 cm of a potentiometer wire. When the cell is shunted by a resistance of 10 Ω, the balancing length is reduced by 20 cm. Find the internal resistance of the cell.
When the null point is obtained in the potentiometer, the current is drawn from the ______
The instrument which can measure terminal potential difference as well as electromotive force (emf) is ______
What is the SI unit of potential gradient?
A potentiometer wire is 4m long and potential difference of 3V is maintained between the ends. The emf of the cell, which balances against a length of 100 cm of the potentiometer wire is ____________.
The potentiometer is more sensitive, when ______.
A potentiometer is an ideal device for measuring potential difference because ______.
Select the WRONG statement:
In the given figure, battery E is balanced on 55 cm length of potentiometer wire but when a resistance of 10 `Omega` is connected in parallel with the battery, then it balances on 50 cm length of the potentiometer wire. The internal resistance r of the battery is ____________.
A potentiometer wire of length 100 cm and resistance 3 `Omega` is connected in series with resistance of 8 `Omega` and an accumulator of 4 volt whose internal resistance is 1 `Omega`.
A wire has a length of 2m and a resistance of 10Ω. It is connected in series with a resistance of 990Ω and a cell of e.m.f. 2V. The potential gradient along the wire will be ______
In the experiment to determine the internal resistance of a cell (E1) using a potentiometer, the resistance drawn from the resistance box is 'R'. The potential difference across the balancing length of the wire is equal to the terminal potential difference (V) of the cell. The value of internal resistance (r) of the cell is ______
Two students X and Y perform potentiometer experiment separately and null point was obtained as shown in diagram. During the experiment, ______.
- X increases the value of R (resistance)
- Y decreases the value of S (resistance)
The position of null point obtained by students X and Y respectively.
A student connected the circuit as shown in the figure to determine the internal resistance of a cell E1 by potentiometer (E > E1). He is unable to obtain the null point because ______.
A potentiometer wire of length 'L' and a resistance 'r' are connected in series with a battery of E.M.F. 'E0' and a resistance 'r1'. A cell of unknown E.M.F, 'E' is balanced at a length 'ℓ' of the potentiometer wire. The unknown E.M.F. E is given by ______
The sensitivity of the potentiometer can be increased by ______.
A potentiometer wire is 100 cm long and a constant potential difference is maintained across it. Two cells are connected in series first to support one another and then in opposite direction. The balance points are obtained at 50 cm and 10 cm from the positive end of the wire in the two cases. The ratio of emf's is ______.
In the experiment of potentiometer, at balance point, there is no current in the ______.
In a potentiometer of 10 wires, the balance point is obtained on the 7th wire. To shift the balance point to 9th wire, we should ______.
AB is a wire of potentiometer with the increase in the value of resistance R, the shift in the balance point J will be ______.
The best instrument for accurate measurement of EMF of a cell is ____________.
What is the current I in the circuit as show in fig.
The instrument among the following which measures the e.m.f of a cell most accurately is ______
Consider a simple circuit shown in figure 
stands for a variable resistance R′. R′ can vary from R0 to infinity. r is internal resistance of the battery (r << R << R0).
- Potential drop across AB is nearly constant as R ′ is varied.
- Current through R′ is nearly a constant as R ′ is varied.
- Current I depends sensitively on R′.
- `I ≥ V/(r + R)` always.
AB is a potentiometer wire (Figure). If the value of R is increased, in which direction will the balance point J shift?
In an experiment with a potentiometer, VB = 10V. R is adjusted to be 50Ω (Figure). A student wanting to measure voltage E1 of a battery (approx. 8V) finds no null point possible. He then diminishes R to 10Ω and is able to locate the null point on the last (4th) segment of the potentiometer. Find the resistance of the potentiometer wire and potential drop per unit length across the wire in the second case.
Two cells of same emf but different internal resistances r1 and r2 are connected in series with a resistance R. The value of resistance R, for which the potential difference across second cell is zero, is ______.
In balanced meter bridge, the resistance of bridge wire is 0.1 Ω cm. Unknown resistance X is connected in left gap and 6 Ω in right gap, null point divides the wire in the ratio 2:3. Find the current drawn from the battery of 5 V having negligible resistance.
A potentiometer wire AB having length L and resistance 12r is joined to a cell D of emf ε and internal resistance r. A cell C having emt `ε/2` and internal resistance 3r is connected. The length AJ at which the galvanometer as shown in the figure shows no deflection is ______.
What is the value of resistance for an ideal voltmeter?
State dimension of potential gradient.
