Practice Electric Charges and Fields NEET PYQ – Free PDF

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Topic Question Set

Q 1 :
A metal cube of side 5 cm is charged with $6$ $μC$ . The surface charge density on the cube is [2024]

$0.125 \times 10^{- 3} C$ $m^{- 2}$
$0.25 \times 10^{- 3} C$ $m^{- 2}$
$4 \times 10^{- 3} C$ $m^{- 2}$
$0.4 \times 10^{- 3} C$ $m^{- 2}$

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(4)

Given, charge $(q) = 6$ $μ C = 6 \times 10^{- 6} C$

Length of cube, $(l) = 5$ $cm = 0.05$ $m$

Total surface area of cube,

$(s) = 6 l^{2} = 6 \times {(10.05)}^{2} = 0.015$ $m^{2}$

Surface charge density, $(σ) = \frac{Total charge}{Total area}$

$= \frac{6 \times 10^{- 6}}{0.015} = 0.4 \times 10^{- 3}$ $c m^{- 2}$

Q 2 :
A spherical conductor of radius 10 cm has a charge of $3.2 \times 10^{- 7} C$ distributed uniformly. What is the magnitude of electric field at a point 15 cm from the centre of the sphere? $(\frac{1}{4 π ε_{0}} = 9 \times 10^{9} {Nm}^{2} / C^{2})$ [2020]

$1.28 \times 10^{4} N/C$
$1.28 \times 10^{5} N/C$
$1.28 \times 10^{6} N/C$
$1.28 \times 10^{7} N/C$

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(2)

Here, $r =$ 10 cm, $q = 3.2 \times 10^{- 7} C$

$E = \frac{k q}{r^{2}} = \frac{9 \times 10^{9} \times 3.2 \times 10^{- 7}}{225 \times 10^{- 4}}$

$E = 1.28 \times 10^{5} N/C$

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