1 Marks Question

Question 511 Mark

Write the formula of Coulomb's law in vacuum or air.

Answer

$\overrightarrow{ F _{12}}=\frac{1}{4 \pi \epsilon_0} \frac{q_1 q_2}{r_{12}^2} r_{12}^{\prime}$
where $\frac{1}{4 \pi \epsilon_0}=9 \times 10^9 Nm ^2 / C ^2$

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Question 521 Mark

What is the minimum possible value of electric charge?

Answer

$e=( \pm) 1.6 \times 10^{-19}$ Coulomb.

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Question 531 Mark

What is the cause of charge?

Answer

Transfer of electrons from one object to another.

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Question 541 Mark

Which forces does a stationary charge produce? If the charge moves with uniform velocity then?

Answer

Stationary charge produces only electric field. A charge moving with uniform velocity produces both electric and magnetic fiels.

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Question 551 Mark

In which activities does the law of conservation of charge apply?

Answer

(i) In nuclear reactions (ii) In pair production process (iii) In friction process.

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Question 561 Mark

What does $q_1+q_2=0$ represent in electrostatics?

Answer

$q_1+q_2=0 \Rightarrow q_1=-q_2 i$ e. $q_1$ and $q_2$ are equal in result and opposite in nature. In electronics it actually refers to charge conservation.

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Question 571 Mark

$q_1$ and $q_2$ are point charges such that $q_1 \times q_2>9$. What is the nature of the force between the two charges?

Answer

Here, $q_1 q_2>0$. This means that $q_1>0$ and $q_2>0$ or $q_1<0, q_2<0$ when both $q_1$ and $q_2$ are positive or negative. Thus, the foree between $q_1$ and $q_2$ will be repulsive.

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Question 581 Mark

Two electrons are kept at a distance of I A from cach other. Calculate the Coulomb force between them.

Answer

$F =\frac{1}{4 \pi \epsilon_0} \times \frac{q_1 q_2}{r^2}$
$=9 \times 10^9 \times \frac{\left(1.6 \times 10^{-19}\right)^2}{\left(10^{-10}\right)^2}$
$=2.3 \times 10^{-8} N$

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Question 591 Mark

If two electric charges $q_1$ and $q_2$ are such that (i) $q_1 q_2>0$, (ii) $q_1 q_2<0$, then what will be the nature of the electric force between them?

Answer

(i) Repulsive (since in this case both the chargers will be of similar nature). (ii) Attractive (since in this case both the charges will be of opposite nature).

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Question 601 Mark

Definition of electric field intensity at a point.

Answer

The electric force acting on a unit test positive charge at any point in the electric field is called the intensity of the electric field at that point.
$E =\lim _{q_0 \rightarrow 0}\left(\frac{F}{q_0}\right)$

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Question 611 Mark

What is the value of the electric field produced by charge $Q$ at any point $\vec{r}$ ?

Answer

$\overrightarrow{ E }=\frac{1}{4 \pi \epsilon_0} \frac{ Q }{r^2} \vec{r}$

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Question 621 Mark

Write Coulomb's law.

Answer

The force of attraction or repulsion (F) between two point charges is proportional to the product of the magnitude of the charges $q_1$ and $q_2$ and inversely proportional to the square of the distance between the charges $\left(1 / r^2\right)$.
That is $F \propto \frac{q_1 q_2}{r^2}$
or $F = K \frac{q_1 q_2}{r^2}$
or $F =\frac{1}{4 \pi \epsilon_o} \frac{q_1 q_2}{r^2}$
Here, $K \left(=\frac{1}{4 \pi \epsilon_{ o }}\right)=9 \times 10^9 Nm ^2 / C ^2$.

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Question 631 Mark

What is the net flux of uniform elecrtric field of Exercise 1.14 through a cube of side 20 cm oriented so that its faces are parallel to the coordinate planes ?

Answer

The net flux through the cube will be zero be-cause the number of lines entering the cube is equal to the number of lines emerging from the surface, that is, as many lines of electric force enter from the face of its 20 cm side as are emerging from it.

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Physics 1 Marks Question