The charges are arranged at the four corners of square $A B C D$ of side ' $d$ ' as shown in figure. The work required to put this arrangement together is given by

$\frac{-9 q^2}{4 \pi \varepsilon_0 d}$
$\frac{-7 q^2}{4 \pi \varepsilon_0 d}$
$\frac{-q^2}{4 \pi \varepsilon_0 d}[9-2 \sqrt{2}]$
$\frac{-q^2}{4 \pi \varepsilon_0 d}[9+2 \sqrt{2}]$
If current ' i ' is passing through the solenoid of diameter ' $d$ ' having number of turns per unit length ' $n$ ', then the inductance per unit length near the middle of a long solenoid is directly proportional to
d and n
$\mathrm{d}^2$ and n
d and $\mathrm{n}^2$
$\mathrm{d}^2$ and $\mathrm{n}^2$
Force is applied to a body of mass 2 kg at rest on a frictionless horizontal surface as shown in the force against time $(\mathrm{F}-\mathrm{t})$ graph. The speed of the body after 1 s is

$2 \mathrm{~m} / \mathrm{s}$
$4 \mathrm{~m} / \mathrm{s}$
$6 \mathrm{~m} / \mathrm{s}$
$10 \mathrm{~m} / \mathrm{s}$
The order of (a) transformer (b) diode rectifier (c) filter (d) voltage regulator in a block diagram of simple rectifier circuit is as
(a) b, d, c, a
(b) a, c, d, b
(c) a, b, c, d
(d) d, c, a, b
d
a
c
b
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