# Blog

### The ratio of electric force between two electrons to two protons separated by the same distance in the air is: A B C D None of these

Correct option is (A) $10^{\circ}$ $\frac{\mathrm{F}_{\mathrm{e}}}{\mathrm{F}_{\mathrm{p}}}=10^{0}=1$, because force depends only on charges, distance and nature of medium and not type of charge. As...

### A cubic solid is made of two elements and Atoms of are at the corners of the cube and at the body-centre. What is the formula of the compound? What are the coordination numbers of and

Ans: It is given that the atoms of $\mathrm{Q}$ are present at the corners of the cube. Therefore, number of atoms of $Q$ in one unit cell $=8 \times(1 / 8)=1$ It is also given that the atoms of...

### A cubic solid is made of two elements and Atoms of are at the corners of the cube and at the body-centre. What is the formula of the compound? What are the coordination numbers of and

Ans: It is given that the atoms of $\mathrm{Q}$ are present at the corners of the cube. Therefore, number of atoms of $Q$ in one unit cell $=8 \times(1 / 8)=1$ It is also given that the atoms of...

### Two particles each of mass and carrying charge are separated by some distance. If they are in equilibrium under mutual gravitational and electrostatic forces, then (in ) is of the order of:

A

B

(C)

D

Correct option is (B) $10^{-10}$ Given : Gravitational force $=$ Electrostatics force Let the distance between the rwo charges be r. $$ \begin{array}{l} \Rightarrow \frac{\mathrm{G}(\mathrm{m})...

### Electrostatic force and gravitational force differ in which respect?

In electrostatic force, the force of medium depends on charges while the force of the medium due to gravity does not depend on masses. There is no concept of induced mass.

### Silver crystallises in the fcc lattice. If edge length of the cell is and density is , calculate the atomic mass of silver.

Ans: It is given that the edge length, $\mathrm{a}=4.07 \times 10^{-8} \mathrm{~cm}$ and density is $\mathrm{d}=$ $10.5 \mathrm{~g} \mathrm{~cm}^{3}$ As the lattice is foc type, the number of atoms...

### Electrostatic force and gravitational force differ in which respect?

A Conservative force,

B Central force

c Principle of superposition

D Dependence on the intervening medium

Correct option is (D) Dependence on the intervening medium In electrostatic force, the force of the medium depends on charges while the force of the medium due to gravity does not depend on masses....

### 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 is :

A 25

B 225

C 625

D 1250

Correct option is (C) 625 We need force of repulsion $=10^{-19} \mathrm{~N}$ Let $n$ no. of increase electrons be placed on each sphere $$ \begin{array}{l} \Rightarrow...

### Copper crystallises into a fcc lattice with edge length . Show that the calculated density is in agreement with its measured value of

Ans: Edge length, $a=3.61 \times 10^{-6} \mathrm{~cm}$ As the lattice is fcc type, the number of atoms per unit cell, $z=4$ Atomic mass, $\mathrm{M}=63.5 \mathrm{~g} \mathrm{~mol}^{-1}$ We also know...

### In comparison to the electrostatic force between two electrons, the electrostatic force between two protons is : A zero B smaller c same D greater

Correct option is(c) same Since the magnitude of the charge of electron and proton is the same, e, the electrostatic force between two protons is the same compared to the electrostatic force between...

### What is a semiconductor? Describe the two main types of semiconductors and contrast their conduction mechanism.

Ans: Semiconductors are substances having conductance in the intermediate range $10^{-6}$ to $10^{4}$ ohm $^{-1} \mathrm{~m}^{-1}$. The two main types of semiconductors are: (i) n-type semiconductor...

### Classify each of the following as being either a -type or an -type semiconductor.

(i) Ge doped with In Ans: Ge (a group 14 element) is doped with In (a group 13 element). Therefore, a hole will be created and the semiconductor generated will be a p-type semiconductor. (ii) B...