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question_answer1)
The n rows each containing m cells in series are joined in parallel. Maximum current is taken from this combination across an external resistance of\[3\Omega \] resistance. If the total number of cells used are 24 and internal resistance of each cell is 0.5 \[\Omega \] then
A)
\[m=8,\,n=3\] done
clear
B)
\[m=6,\,n=4\] done
clear
C)
\[m=12,\,n=2\] done
clear
D)
\[m=2,\,n=12\] done
clear
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question_answer2)
Two wires each of radius of cross section r but of different materials are connected together end to end (i.e. in series). If the densities of charge carriers in the two wires are in the ratio 1:4, the drift velocity of electrons in the two wires will be in the ratio
A)
1 : 2 done
clear
B)
2 : 1 done
clear
C)
4 : 1 done
clear
D)
1 : 4 done
clear
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question_answer3)
A wire of cross-section area A, length \[{{L}_{1}}\] resistivity \[{{\rho }_{1}}\] and temperature coefficient of resistivity \[{{\alpha }_{1}}\] is connected in series to a second wire of length \[{{L}_{2}}\] resistivity \[{{\rho }_{2}}\], temperature coefficient of resistivity \[{{\alpha }_{2}}\]and the same are A, so that wires carry same current. Total resistance R is independent of temperature for small temperature change if (Thermal expansion effect is negligible)
A)
\[{{\alpha }_{1}}=\,-{{\alpha }_{2}}\] done
clear
B)
\[{{\rho }_{1}}{{L}_{1}}{{\alpha }_{1}}+{{\rho }_{2}}{{L}_{2}}{{\alpha }_{2}}=0\] done
clear
C)
\[{{L}_{1}}{{\alpha }_{1}}+{{L}_{2}}{{\alpha }_{2}}=0\] done
clear
D)
None of these done
clear
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question_answer4)
The plot represents the flow of current through a wire at three different times. The ratio of charges flowing through the wire at different times is (see figure)
A)
2 : 1 : 2 done
clear
B)
1 : 3 : 3 done
clear
C)
1 : 1 : 1 done
clear
D)
2 : 3 : 4 done
clear
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question_answer5)
Find the equivalent resistance between A and B. Each resistor has same resistance R.
A)
\[\frac{8}{5}R\] done
clear
B)
\[\frac{6}{5}R\] done
clear
C)
\[\frac{7}{5}R\] done
clear
D)
\[\frac{4}{5}R\] done
clear
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question_answer6)
A network of twelve resistances each of resistance R form a square of squares as shown in the figure. The outer square is fitted in a metal ring of negligible resistance. Find the resistance between centre of the square and the ring.
A)
R/4 done
clear
B)
R/2 done
clear
C)
3R/8 done
clear
D)
R/12 done
clear
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question_answer7)
Find the equivalent resistance. across the terminals of source of e.m.f. 24 V for the circuit shown in figure
A)
\[15\Omega \] done
clear
B)
\[10\Omega \] done
clear
C)
\[5\Omega \] done
clear
D)
\[4\Omega \] done
clear
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question_answer8)
In the part of a circuit shown in figure, the potential difference \[({{V}_{G}}-{{V}_{H}})\]between points G and H will be
A)
0V done
clear
B)
15V done
clear
C)
7V done
clear
D)
3V done
clear
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question_answer9)
For the arrangement shown in figure, the switch is closed at t = 0. The time after which the current becomes \[2.5\mu A\]is given by (take ln2 = 0.69)
A)
10 s done
clear
B)
5 s done
clear
C)
7 s done
clear
D)
0.693 s done
clear
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question_answer10)
In order to determine the e.m.f. of a storage battery it was connected in series with a standard cell (both are adding) in a certain circuit and a current \[{{I}_{1}}\] was obtained. When polarity of the standard cell is reversed, a current \[{{I}_{2}}\] was obtained in the same direction as that of \[{{I}_{1}}\] what is the e.m.f. \[{{\varepsilon }_{1}}\] of the storage battery? The e.m.f. of the standard cell is\[{{\varepsilon }_{2}}\].
A)
\[{{\varepsilon }_{1}}=\frac{{{I}_{1}}+{{I}_{2}}}{{{I}_{1}}-{{I}_{2}}}{{\varepsilon }_{2}}\] done
clear
B)
\[{{\varepsilon }_{1}}=\frac{{{I}_{1}}+{{I}_{2}}}{{{I}_{2}}-{{I}_{1}}}{{\varepsilon }_{2}}\] done
clear
C)
\[{{\varepsilon }_{1}}=\frac{{{I}_{1}}-{{I}_{2}}}{{{I}_{1}}+{{I}_{2}}}{{\varepsilon }_{2}}\] done
clear
D)
\[{{\varepsilon }_{1}}=\frac{{{I}_{2}}-{{I}_{1}}}{{{I}_{1}}+{{I}_{2}}}{{\varepsilon }_{2}}\] done
clear
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question_answer11)
The length of a given cylindrical wire is increased by 100% Due to the consequent decrease in diameter, the change in the resistance of the wire will be
A)
300% done
clear
B)
200% done
clear
C)
100% done
clear
D)
50% done
clear
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question_answer12)
A resistor 'R' and \[2\,\mu F\] capacitor in series is connected through a switch to 200 V direct supply. Across the capacitor is a neon bulb that lights up at 120 V. Calculate the value of R to make the bulb light up 5 s after the switch has been closed. \[(lo{{g}_{10}}2.5=0.4)\]
A)
\[1.3\times {{10}^{4}}\Omega \] done
clear
B)
\[1.7\times {{10}^{5}}\Omega \] done
clear
C)
\[2.7\times {{10}^{6}}\Omega \] done
clear
D)
\[3.3\times {{10}^{7}}\Omega \] done
clear
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question_answer13)
When 5V potential difference is applied across a wire of length 0.1 m, the drift speed of electrons is \[2.5\times {{10}^{-4}}m{{s}^{-1}}\] If the electron density in the wire is \[8\times {{10}^{28}}{{m}^{-3}}s\], the resistivity of the material is close to
A)
\[1.6\times {{10}^{-8}}\Omega \,m\] done
clear
B)
\[1.6\times {{10}^{-7}}\Omega \,m\] done
clear
C)
\[1.6\times {{10}^{-6}}\Omega \,m\] done
clear
D)
\[1.6\times {{10}^{-5}}\Omega \,m\] done
clear
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question_answer14)
Two capacitors \[{{C}_{1}}\] and \[{{C}_{2}}\] \[({{C}_{1}}>{{C}_{2}})\] are charged separately to same potential. Now they are allowed to discharge through similar resistors. Initial rate of discharging will be
A)
More for \[{{C}_{1}}\] done
clear
B)
More for \[{{C}_{2}}\] done
clear
C)
Same for both done
clear
D)
Cannot say done
clear
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question_answer15)
For a cell, a graph is plotted between the potential Difference V across the terminals of the cell and the current \[I\] drawn from the cell (see figure). The emf and the internal resistance of the cell are E and r respectively. Then
A)
\[E=2V,\,r=0.5\,\Omega \] done
clear
B)
\[E=2V,\,r=0.4\,\Omega \] done
clear
C)
\[E>2V,\,r=0.5\,\Omega \] done
clear
D)
\[E>2V,\,r=0.4\,\Omega \] done
clear
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question_answer16)
The effective resistance between points P and Q of the electrical circuit shown in the figure is
A)
\[2Rr/(R+r)\] done
clear
B)
\[8R(R+r)(3R+r)\] done
clear
C)
\[2r+4R\] done
clear
D)
\[5R/2+2r\] done
clear
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question_answer17)
Two conductors AB and CD are connected between two parallel resistors in such a way that no current flows through them. Then a wire is connected between E and F.
A)
There is no current in EF done
clear
B)
Current flows from E to F done
clear
C)
Current flows F to E done
clear
D)
None of these done
clear
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question_answer18)
A battery of emf \[{{E}_{0}}=12\,V\] is connected across a 4 m long uniform wire having resistance \[\frac{4\Omega }{m}\] the cells of small m emfs \[{{\varepsilon }_{1}}=2\,V\] and \[{{\varepsilon }_{2}}=4\,V\] having internal resistance 2\[\Omega \] and 6\[\Omega \] respectively, are connected as shown in the figure. If galvanometer shows no deflection at the point N, the distance of point N from the point A is equal to
A)
\[\frac{1}{6}m\] done
clear
B)
\[\frac{1}{3}m\] done
clear
C)
\[25m\] done
clear
D)
\[50m\] done
clear
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question_answer19)
The temperature coefficient of resistance of conductor varies as\[\alpha (T)=3{{T}^{2}}+2T\]. If \[{{R}_{0}}\] is resistance at T= 0 and R is resistance at T, then
A)
\[R={{R}_{0}}(6T+2)\] done
clear
B)
\[R=2{{R}_{0}}(3+2T)\] done
clear
C)
\[R={{R}_{0}}(1+{{T}^{2}}+{{T}^{3}})\] done
clear
D)
\[R={{R}_{0}}(1-T+{{T}^{2}}+{{T}^{3}})\] done
clear
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question_answer20)
For comparing the e.m.f.'s of two cells with a potentiometer, a standard cell is used to develop a potential gradient along the wires. Which of the following possibilities would make the experiment unsuccessful?
A)
The e.m.f. of the standard cell is larger than the E e.m.f.'s of the two cells done
clear
B)
The diameter of the wires is the same and uniform throughout done
clear
C)
The number of wires is ten done
clear
D)
The e.m.f. of the standard cell is smaller than the e.m.f.'s of the two cells done
clear
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question_answer21)
The potential difference across 8 ohm resistance is 48 volt as shown in the figure. What is the value of potential difference (in V) across A" and Y points?
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question_answer22)
In order to quadruple the resistance of a uniform wire, a part of its length was uniformly stretched till the final length of the entire wire was 1.5 times the original length, the part of the wire was fraction equal to ______.
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question_answer23)
A battery of internal resistance 4\[\Omega \] is connected to the network of resistances as shown. In order to give the maximum power to the network, the value of equivalent resistance (in\[\Omega \].) should be ______ R.
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question_answer24)
In an experiment to measure the internal resistance of g cell by potentiometer, it is found that the balance point is at a length of 2m when the cell is shunted by a 5\[\Omega \] resistance; and is at a length of 3m when the cell is shunted by a 10\[\Omega \]. resistance. What is the internal resistance (in\[\Omega \]) of the cell?
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question_answer25)
A resistance of 4\[\Omega \] and a wire of length 5 metres and resistance 5\[\Omega \] are joined in series and connected to a cell of e.m.f. 10 V and internal resistance 1\[\Omega \] parallel combination of two identical cells is balanced across 300 cm of the wire. The e.m.f. E of each cell is (in V)_______.
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