Two batteries of e.m.f. 4V and 8 V with internal resistances 1 Ω and 2 Ω are connected in a circuit with a resistance of 9 Ω as shown in figure. The current and potential difference between the points P and Q are
13A and 3V
16A and 4V
19A and 9V
12A and 12V
Four identical cells each having an electromotive force (e.m.f.) of 12V, are connected in parallel. The resultant electromotive force (e.m.f.) of the combination is :
48 V
12 V
4 V
3 V
The internal resistance of a cell of e.m.f. 12V is 5×10−2 Ω. It is connected across an unknown resistance. The voltage across the cell, when a current of 60 A is drawn from it, is :
15 V
9 V
6 V
The current in the given circuit is
0.1 A
0.2 A
0.3 A
0.4 A
Consider four circuits shown in the figure below. In which circuit power dissipated is greatest (Neglect the internal resistance of the power supply)
In the circuit, the reading of the ammeter is (assume internal resistance of the battery be zero) :
4029A
109A
53A
2 A
Eels are able to generate current with biological cells called electroplaques. The electroplaques in an eel are arranged in 100 rows, each row stretching horizontally along the body of the fish containing 5000 electroplaques. The arrangement is suggestively shown below. Each electroplaques has an emf of 0.15 V and internal resistance of 0.25 Ω
The water surrounding the eel completes a circuit between the head and its tail. If the water surrounding it has a resistance of 500 Ω, the current an eel can produce in water is about
(1) 5 A
(2) 3.0 A
(3) 15 A
(4) 30 A
A battery is charged at a potential of 15 V for 8 hours when the current flowing is 10 A. The battery on discharge supplies a current of 5 A for 15 hours. The mean terminal voltage during discharge is 14 V. The "Watt-hour" efficiency of the battery is :
82.5%
80 %
90%
87.5%
A capacitor is connected to a cell of emf E having some internal resistance r. The potential difference in steady state across the
Cell is < E
Cell is E
Capacitor is > E
Capacitor is < E
The maximum power drawn out of the cell from a source is given by (where r is internal resistance)
E2/r
E2/2r
E2/4r
E2/3r
Find out the value of current through 2Ω resistance for the given circuit
5 A
Zero
4 A
Two sources of equal emf are connected to an external resistance R. The internal resistances of the two sources are R1 and R2 (R2>R1). If the potential difference across the source having internal resistance R2 is zero, then
R=R1R2/(R1+R2)
R=R1R2/(R2−R1)
R=R2×(R1+R2)/(R2−R1)
R=R2−R1
The magnitude of i in ampere unit is
0.1
0.3
0.6
None of these
To draw maximum current from a combination of cells, how should the cells be grouped
Series
Parallel
Mixed
Depends upon the relative values of external and internal resistance
By ammeter, which of the following can be measured
Electric potential
Potential difference
Current
Resistance
The resistance of 1 A ammeter is 0.018 Ω. To convert it into 10 A ammeter, the shunt resistance required will be :
0.18 Ω
0.0018 Ω
0.002 Ω
0.12 Ω
For measurement of potential difference, the potentiometer is preferred in comparison to the voltmeter because:
the potentiometer is more sensitive than the voltmeter.
the resistance of the potentiometer is less than the voltmeter.
the potentiometer is cheaper than the voltmeter.
the potentiometer does not take current from the circuit.
The potential gradient along the length of a uniform wire is 10 volt/metre. B and C are the two points at 30 cm and 60 cm point on a meter scale fitted along the wire. The potential difference between B and C will be :
3 volt
0.4 volt
7 volt
4 volt
In Wheatstone's bridge P = 9 ohm, Q = 11 ohm, R = 4 ohm and S = 6 ohm. How much resistance must be put in parallel to the resistance S to balance the bridge
24 ohm
449ohm
26.4 ohm
18.7 ohm
A potentiometer is an ideal device of measuring potential difference because
It uses a sensitive galvanometer
It does not disturb the potential difference it measures
It is an elaborate arrangement
It has a long wire hence heat developed is quickly radiated
A battery of 6 volts is connected to the terminals of a three metre long wire of uniform thickness and resistance of the order of 100 Ω. The difference of potential between two points separated by 50cm on the wire will be :
1 V
1.5 V
2 V
A potentiometer is used for the comparison of e.m.f. of two cells E1 and E2. For cell E1 the no deflection point is obtained at 20cm and for E2 the no deflection point is obtained at 30cm. The ratio of their e.m.f.'s will be
2/3
1/2
1
2
If the length of the potentiometer wire is increased, then the length of the previously obtained balance point will :
Increase
Decrease
Remain unchanged
Become two times
If in the experiment of Wheatstone's bridge, the positions of cells and galvanometer are interchanged, then balance points will
Change
Depend on the internal resistance of cell and resistance of galvanometer
Two cells when connected in series are balanced on 8m on a potentiometer. If the cells are connected with polarities of one of the cells reversed, they balance on 2m. The ratio of e.m.f.'s of the two cells is
3 : 5
5 : 3
3 : 4
4 : 3
In the diagram shown, the reading of voltmeter is 20 V and that of ammeter is 4 A. The value of R should be (consider given ammeter and voltmeter are not ideal) :
Equal to 5 Ω
Greater from 5 Ω
Less than 5 Ω
Greater or less than 5 Ω depends on the material of R
Which is a wrong statement :
The Wheatstone bridge is most sensitive when all the four resistances are of the same order
In a balanced Wheatstone bridge, interchanging the positions of galvanometer and cell affects the balance of the bridge
Kirchhoff's first law (for currents meeting at a junction in an electric circuit) expresses the conservation of charge
The rheostat can be used as a potential divider
AB is a wire of uniform resistance. The galvanometer G shows no current when the length AC = 20cm and CB = 80 cm. The resistance R is equal to
2 Ω
8 Ω
20 Ω
40 Ω
The circuit shown here is used to compare the e.m.f. of two cells E1 and E2(E1>E2). The null point is at C when the galvanometer is connected to E1. When the galvanometer is connected to E2, the null point will be
To the left of C
To the right of C
At C itself
Nowhere on AB
In the Wheatstone's bridge (shown in the figure) X = Y and A > B. The direction of the current between a and b will be:
from a to b.
from b to a.
from b to a through c.
from a to b through c.
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