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If copper and silicon pieces are heated, the resistance of

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Important Questions on Current Electricity

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The potential difference between points A and B of adjoining figure is

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Consider four conducing materials copper, tungsten, mercury and aluminum with resistivity ρC, ρT, ρM and ρA respectively. Then :
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Electric field and current density have relation
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Brown, Red and Orange coloured bands on a Carbon resistor are followed by silver band. The value of resistor is ________.
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If the valence electrons exactly fill one or more bands, leaving other empty, then the crystal will be 
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A conductor carries a current of 300 mA. The number of electrons passing through it in 1 minute are ___ .
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Which of the following acts as a circuit protective device?
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A steady current I is set up in a wire whose cross-sectional area decreases in the direction of the flow of the current. Then, as we examine the narrowing region,


 
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Resistance of a carbon resistor determined from colour codes is (22000±5%) Ω. The colour of the third band must be :
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A solar cell is to be fabricated for efficient conversion of solar radiation to emf using material A. The solar cell is to be mechanically protected with the help of a coating using material B. If the band gap energy of materials A and B are EA and EB respectively, then which of the following choices is optimum for better performance of the solar cell.
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When light shines on a p-n junction diode, the current I versus voltage V is observed as in figure below.

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In which quadrant(s) does the diode generate power, so that it can be used as a solar cell?

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A circular wire has current density J=2×1010Am2r2 where r is the radial distance, out of the wire radius is 2 mm. The end-to-end potential applied to the wire is 50 V. How much energy (in joule) is converted to thermal energy in 100 s?
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The difference between the maximum and minimum values of resistance of a resistor with the color scheme green-green-red-silver is
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Estimate the magnitude of current that passes through a wire, if 0.1 mol of electrons flow through it in 40 min. (Assume Avogadro number =6×1023)
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A current through a wire depends on time as i=α0t+βt2, where α0=20 A s-1 and β=8 A s-2. Find the charge crossed through a section of the wire in 15 s.
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The current in a conductor varies with time t as I=2t+3t2, where I is in ampere and t in seconds. Electric charge flowing through a section of the conductor during t=2 sec to t=3 sec is
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Across a metallic conductor of non-uniform cross section a constant potential difference is applied. The quantity which remains constant along the conductor is:
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Two copper wires of length l and 2 l have radii r and 2 r respectively. The ratio of their specific resistances is.
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The n-side of the depletion layer of a p-n junction