Download 1/6 1 State the principle of a potentiometer. Name two

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Name of Student:
NAME OF UNIT: ELECTRIC CURRENT
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GRADE XII
SUBJECT: PHYSICS
WORKSHEET NO:3
State the principle of a potentiometer.
Name two factors that decide the
sensitivity of a potentiometer. Explain
with reason how the balance point shift
when (a) R is increased (b) S is
increased (c) emf of cell Q is greater
than that of cell P (d) Cell P is replaced
by another cell of lower emf (e)
connecting a resistance parallel to Q (in
each case assume other factors to be
constant.)
Calculate the value of the resistance R in the circuit
shown in the figure so that the current in the circuit is 0.2
A. What would be the potential difference between points
A and B?
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Which one you prefer to measure the emf of a cell, voltmeter or potentiometer, why?
In the figure a long uniform potentiometer wire
AB is having a constant potential gradient alongits
length. The null points for the two primary cells of
emfs E1and E2 connected in the manner shown
are obtained at a distance of 120 cm and 300 cm
from the end A. Find (i) E1 / E2 and (ii) position of
null point for the cell E1. How is the sensitivity of
a potentiometer increased?
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In the circuit shown, R1 = 4 Ω, R2 = R3 = 5
Ω, R4 = 10Ω and E = 6V. Work out the
equivalent resistance of the circuit and the
current in each resistor.
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Two cells E1 and E2 of EMF’s 5 V and 9 V and internal resistances of 0.3Ω and 1.2Ω
respectively are connected to a network of resistances as shown in the figure. Calculate
the value of current flowing through the 3Ω resistance.
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Three cells of e.m.f., E1 = 1.5 V, E2 = 2.0 V and E3 = 3 V, having internal resistances r1
= 0.3 Ω, r2 = 0.4 Ω and r3 = 0.6 Ω respectively are connected in parallel and then in
series. Find out the equivalent e.m.f. and the equivalent resistance of a cell which can
replace the series and parallel combination.
Explain with reason the change in brightness of the bulbs, if any , if the resistance of the
rheostat is increased.
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In the meter bridge experimental set up,
shown in the figure, the null point ‘D’ is
obtained at a distance of 40 cm from end A
of the meter bridge wire. If a resistance of
10 Ω is connected in series with R1, null
point is obtained at AD = 60 cm. Calculate
the value of R1 and R2.
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When the galvanometers in each
arrangement do not show any deflection,
obtain the ratio R1 / R2 .
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A resistance R =5Ω is connected to one of the gaps
in a metre bridge, which uses a wire of length 1 m.
An unknown resistance X is connected in the other
gap as shown in the figure. The balance point is
noticed at ‘l’ cm from the positive end of the battery.
On interchanging R and X, it was found that the
balance point further shifts by 20 cm away from
end A. Neglecting the end correction, calculate the
valueof unknown resistance X used.
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A potentiometer wire of length 1 m is connected to a
driver cell of emf 3 V as shown in the figure. When a
cell of 1.5 V emf is used in the secondary circuit, the
balance point is found to be 60 cm. On replacing this
cell and using a cell of unknown emf, the balance
point shifts to 80 cm. Calculate the unknown emf .
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Two wires X, Y have the same resistivity, but their cross-sectional areas are in the ratio
2 : 3 and lengths in the ratio 1 : 2. They are first connected in series and then in parallel
to a d.c. source. Find out the ratio of the drift speeds of the electrons in the two wires
for the two cases.
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Calculate the value of the unknown potential V
for the given potentiometer circuit. The total
length (400 cm) of the potentiometer wire has a
resistance of 10 Ω and the balance point is
obtained at a length of 240 cm.
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The plot of the variation of potential difference across a
combination of three identical cells in series, versus current
is as shown below. What is the emf of each cell ?
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Calculate the current drawn from the battery in the given network.
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