Advertisements
Advertisements
Question
A cell of e.m.f 1.5V and negligible internal resistance is connected in series with a potential meter of length 10 m and the total resistance of 20 Ω. What resistance should be introduced in the resistance box such that the potential drop across the potentiometer is one microvolt per cm of the wire?
Solution
Given:
R = 20 Ω, L = 10 m, E = 1.5 V,
K = 1 μV/cm = 1 × (10-6 /10-2 ) V/ m
= 10-4 V/ m
To find: External resistance (RE)
Formula: K = `"V"/"L"`
Calculation:
Since, I = `"E"/("R" + "R"_"E")`
Also, V = IR = `"ER"/("R" + "R"_"E")`
From formula,
K = `"ER"/(("R" + "R"_"E")"L")`
R + RE = `"ER"/"KL"`
∴ RE = `(1.5 xx 20)/(10^-4 xx 10) - 20 = 30000 - 20`
∴ RE = 29980 Ω
The external resistance should be 29980 Ω.
APPEARS IN
RELATED QUESTIONS
Write two factors by which current sensitivity of a potentiometer can be increased.
On what factors does the potential gradient of the wire depend?
State the advantages of potentiometer over voltmeter.
In a potentiometer experiment, balancing length is found to be 120 cm for a cell E1 of emf 2V. What will be the balancing length for another cell E2 of emf 1.5V? (No other changes are made in the experiment.)
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.
Figure shows a long potentiometer wire AB having a constant potential gradient. The null points for the two primary cells of emfs ε1 and ε2 connected in the manner shown are obtained at a distance of l1 = 120 cm and l2 = 300 cm from the end A. Determine (i) ε1/ε2 and (ii) position of null point for the cell ε1 only.
Describe briefly, with the help of a circuit diagram, how a potentiometer is used to determine the internal resistance of a cell.
Would you prefer a voltmeter or a potentiometer to measure the emf of a battery?
State the uses of a potentiometer.
What will be the effect on the position of zero deflection if only the current flowing through the potentiometer wire is increased?
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 battery of emf 4 volt and internal resistance 1 Ω is connected in parallel with another battery of emf 1 V and internal resistance 1 Ω (with their like poles connected together). The combination is used to send current through an external resistance of 2 Ω. Calculate the current through the external resistance.
A potential drop per unit length along a wire is 5 × 10−3 V/m. If the emf of a cell balances against length 216 cm of this potentiometer wire, find the emf of the cell.
The resistance of a potentiometer wire is 8 Ω and its length is 8 m. A resistance box and a 2 V battery are connected in series with iL What should be the resistance in the box if it is desired to have a potential drop of 1 µV/mm?
The instrument which can measure terminal potential difference as well as electromotive force (emf) is ______
State any one use of a potentiometer.
What are the disadvantages of a potentiometer over a voltmeter?
A 10 m long wire of resistance 20 Q is connected in series with a battery of emf 3 V and a resistance of 10 Ω. The potential gradient along the wire in V/m is ________.
The potentiometer is more sensitive, when ______.
Two cells when connected in series are balanced on 8 m on a potentiometer. If the cells are connected with polarities of one of the cell reversed, they balance on 2 m. The ratio of e.m.f's of the two cells is ____________.
Which of the following is true for a potentiometer?
Sensitivity of a given potentiometer can be decreased by ______.
A potentiometer wire of length 100 cm has a resistance of 10 `Omega.` It is connected in series with a resistance and an accumulator of e.m.f 2 V and of negligible internal resistance. A source of e.m.f 10 mV is balanced against a 40 cm length of the potentiometer wire. The value of the external resistance is ____________.
The length of a wire of a potentiometer is 100 cm, and the e.m.f of its standard cell is E volt. It is employed to measure the e.m.f of a battery whose internal resistance is 0.5 `Omega` If the balance point is obtained at `l`= 30 cm from the positive end, the e.m.f of the battery is ____________.
where 'i' is the current in the potentiometer
A potentiometer wire is 10 m long and has resistance of 2`Omega`/m. It is connected in series with a battery of e.m.f 3 V and a resistance of 10 `Omega`. The potential gradient along the wire in V/m is ______.
If the length of potentiometer wire is increased, then the length of the previously obtained balance point will ______.
In a potentiometer experiment when three cells A, B, C are connected in series the balancing length is found to be 740 cm. If A and B are connected in series, the balancing length is 440 cm and when B and C are connected in series, it is 540 cm. The e.m.f. of A, B, and C cells EA, EB, EC are respectively (in volt) ______
In a potentiometer experiment, for measuring internal resistance of a cell, the balance point has been obtained on the fourth wire. The balance point can be shifted to fifth wire by ______.
A battery is connected with a potentiometer wire. The internal resistance of the battery is negligible. If the length of the potentiometer wire of the same material and radius is doubled then ______.
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 ____________.
A 10 m long wire of uniform cross-section and 20 Ω resistance is used in a potentiometer. The wire is connected in series with a battery of 5 V along with an external resistance of 480 Ω. If an unknown emf E is balanced at 6.0 m length of the wire, then the value of unknown emf is ______.
Three resistance each of 4Ω are connected to from a triangle. The resistance b / w two terminal is
The value of current I in the network shown in fig.
A wire of resistance R is cut into two equal part. There parts are then connected in parallel. The equivalent resistance of the combination will be
What is the current I in the circuit as show in fig.
1°C rise in temperature is observed in a conductor by passing a certain current. If the current is double then the rise in temperature is approximately.
In a potentiometer circuit, a cell of EMF 1.5 V gives balance point at 36 cm length of wire. If another cell of EMF 2.5 V replaces the first cell, then at what length of the wire, the balance point occurs?
AB is a potentiometer wire (Figure). If the value of R is increased, in which direction will the balance point J shift?
For the circuit shown, with R1 = 1.0 Ω, R2 = 2.0 Ω, E1 = 2 V, and E2 = E3 = 4 V, the potential difference between the points 'a' and 'b' is approximately (in V) ______.
Potential difference between the points A and B in the circuit shown is 16 V, then potential difference across 2Ω resistor is ______ V. volt. (VA > VB)
As a cell age, its internal resistance increases. A voltmeter of resistance 270 Ω connected across an old dry cell reads 1.44 V. However, a potentiometer at the balance point gives a voltage measurement of the cell as 1.5 V. Internal resistance of the cell is ______ Ω.
If you are provided a set of resistances 2Ω, 4Ω, 6Ω and 8Ω. Connect these resistances so as to obtain an equivalent resistance of `46/3`Ω.
A cell of internal resistance r is connected across an external resistance nr. Then the ratio of the terminal voltage to the emf of the cell is ______.
In potentiometer experiment, null point is obtained at a particular point for a cell on potentiometer wire x cm long. If the length of the potentiometer wire is increased without changing the cell, the balancing length will ______. (Driving source is not changed)
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 will a voltmeter of resistance 200 Ω read when connected across a cell of emf 2 V and internal resistance 2 Ω?
