What is the force between two small charged spheres having charges of $2 \times 1 0^{- 7}$ C and $3 \times 1 0^{- 7}$ C placed 30 cm apart in air?

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Answer 1

Charge on the first sphere, $q_{1} = 2 \times 1 0^{- 7}$ C
Charge on the second sphere, $q_{2} = 3 \times 1 0^{- 7}$ C
Distance between the spheres, $r = 30 c m = 0.3 m$
$F = \frac{q _{1} q _{2}}{4 π ε _{0} r ^{2}}$
Where, $ε_{0} =$ Permittivity of free space

$\frac{1}{4 π ε _{0}} = 9 \times 1 0^{9} N m^{2} C^{- 2}$
$F = \frac{9 \times 1 0 ^{9} \times 2 \times 1 0 ^{- 7} \times 3 \times 1 0 ^{- 7}}{( 0 . 3 ) ^{2}} = 6 \times 1 0^{- 3} N$
Hence, force between the two small charged spheres is $6 \times 1 0^{- 3}$ N. The charges are of same nature. Hence, force between them will be repulsive.

Answer 2

Charge on the first sphere, $q_{1} = 2 \times 1 0^{- 7}$ C

Charge on the second sphere, $q_{2} = 3 \times 1 0^{- 7}$ C

Distance between the spheres, $r = 30 c m = 0.3 m$

$F = \frac{q _{1} q _{2}}{4 π ε _{0} r ^{2}}$

Where, $ε_{0} =$ Permittivity of free space

$\frac{1}{4 π ε _{0}} = 9 \times 1 0^{9} N m^{2} C^{- 2}$

$F = \frac{9 \times 1 0 ^{9} \times 2 \times 1 0 ^{- 7} \times 3 \times 1 0 ^{- 7}}{( 0 . 3 ) ^{2}} = 6 \times 1 0^{- 3} N$

Hence, force between the two small charged spheres is $6 \times 1 0^{- 3}$ N. The charges are of same nature. Hence, force between them will be repulsive.

What is the force between two small charged spheres having charges of $2 \times 1 0^{- 7}$ C and $3 \times 1 0^{- 7}$ C placed 30 cm apart in air?

Two small spheres each of radius 1 mm are kept 10 cm apart. Assuming each proton has a charge +e and each electron has a charge 0.1% less than +e then find the force between the two spheres. Density of copper is 8.9 gcm $^{- 3}$ and atomic mass number is 63.5.

A charge of $10$ $u n i t s$ is divided so that force between the two charges is maximum when placed $2$ $c m$ apart. The two charges are:

The excess (equal in number) number of electrons that must be placed on each of the two small spheres spaced $3 c m$ apart with a force of repulsion between them to be $1 0^{- 19} N$ is :

When two magnetic poles one of which is four times greater than the other in pole strength, are placed 5 cm apart in air. They exert a mutual force of 144 mg.wt. on each other. The pole strengths of the poles are (in ampere metre)
(g=10 m/s $^{2}$ )

Revise with Concepts

Coulomb's Law - Problem L1

What is the force between two small charged spheres having charges of 2×10−7C and 3×10−7C placed 30 cm apart in air?

Two small spheres each of radius 1 mm are kept 10 cm apart. Assuming each proton has a charge +e and each electron has a charge 0.1% less than +e then find the force between the two spheres. Density of copper is 8.9 gcm−3 and atomic mass number is 63.5.

A charge of 10 units is divided so that force between the two charges is maximum when placed 2 cm apart. The two charges are:

The excess (equal in number) number of electrons that must be placed on each of the two small spheres spaced 3cm apart with a force of repulsion between them to be 10−19N is :

When two magnetic poles one of which is four times greater than the other in pole strength, are placed 5 cm apart in air. They exert a mutual force of 144 mg.wt. on each other. The pole strengths of the poles are (in ampere metre) (g=10 m/s2)

Revise with Concepts

Coulomb's Law - Problem L1

What is the force between two small charged spheres having charges of $2 \times 1 0^{- 7}$ C and $3 \times 1 0^{- 7}$ C placed 30 cm apart in air?

Two small spheres each of radius 1 mm are kept 10 cm apart. Assuming each proton has a charge +e and each electron has a charge 0.1% less than +e then find the force between the two spheres. Density of copper is 8.9 gcm $^{- 3}$ and atomic mass number is 63.5.

A charge of $10$ $u n i t s$ is divided so that force between the two charges is maximum when placed $2$ $c m$ apart. The two charges are:

The excess (equal in number) number of electrons that must be placed on each of the two small spheres spaced $3 c m$ apart with a force of repulsion between them to be $1 0^{- 19} N$ is :

When two magnetic poles one of which is four times greater than the other in pole strength, are placed 5 cm apart in air. They exert a mutual force of 144 mg.wt. on each other. The pole strengths of the poles are (in ampere metre)
(g=10 m/s $^{2}$ )