Two metallic spheres of radii 1 ~cm and 3 ~cm are given charges of -1 × 10^ -2 C and 5 × 10^ -2 C , respectively. If these are connected by a conducting wire, the final charge on the bigger sphere is

Correct answer: B. 3 × 10^ -2 C Charge flows from high potential to low potential aligned (K Q_1)/(3)& =(K Q_2)/(1) Q_1 & =3 Q_2 aligned Also aligned Q_1+Q_2 & =4 ×10^ -2 4 Q_2 & =4 ×10^ -2 aligned Q_2=10^ -2 and Q_1=3 × 10^ -2 C

NEET 2012

Exam: NEET
Year: 2012
Subject: Physics
Chapter: Electrostatics

NEET 2012 · Physics · Electrostatics

Two metallic spheres of radii 1 ~cm and 3 ~cm are given charges of...

Two metallic spheres of radii

1 \mathrm{~cm}

and

3 \mathrm{~cm}

are given charges of

-1 \times 10^{-2} \mathrm{C}

and

5 \times 10^{-2} \mathrm{C}

, respectively. If these are connected by a conducting wire, the final charge on the bigger sphere is

Options

A $2 \times 10^{-2} \mathrm{C}$
B $3 \times 10^{-2} \mathrm{C}$
C $4 \times 10^{-2} \mathrm{C}$
D $1 \times 10^{-2} \mathrm{C}$

Correct answer

B. $3 \times 10^{-2} \mathrm{C}$

Step-by-step solution

Charge flows from high potential to low potential

\begin{aligned}\frac{K Q_1}{3}& =\frac{K Q_2}{1}\\ Q_1 & =3 Q_2 \end{aligned}

Also

\begin{aligned}Q_1+Q_2 & =4 \times10^{-2} \\ 4 Q_2 & =4 \times10^{-2} \end{aligned}

Q_2=10^{-2} and

\quad Q_1=3 \times 10^{-2} \mathrm{C}

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