Conductors and Insulators

Q. What is the minimum electrical force between two charged particles 1 m apart in free space? what must be the charges should it be charge of electron??

Q. Two small conducting spheres of equal radius have charges +10microcoloumb and -20microcoloumb respectively and placed at a distance R from each other.They experience force F₁ if they are brought in contact and separated to the same distance, they experience force F₂ . Then the ratio of F₁ and F₂ will be?

Q.

What is the difference between electricity and current?

Q. Electric field due to uniformly charged conducting sheet? Electric field due to uniformly charged non conducting sheet?

Q. (Q.)two non conducting solid spheres of radii R and 2R having uniform volume charge densities ρ1 and ρ2 respectively, touch each other .the net electric field at a a distance 2R from the centre of the smaller sphere , along the line joining the centres of the spheres , is zero .the ratio of ρ1/ρ2 can be a)-4 b)32/25 c)4 d)-32/25

Q. Two identical metal spheres possess +60c & -20c of charges. They are brought in contact &then separated by 10cm. The force between them is

Q. N fundamental charges each of charge q are to be distributed as two point charges separated by a fixed dis†an ce , then the maximum to minimum force bears a ratio (N is even and greater than 2)

Q. A neutral metal sphere is touched by a negatively charged metal rod. During the process, electrons are transferred from the ______ to the ______ and the sphere acquires a ______ charge.

1. neutral sphere, charged rod, negative
2. neutral sphere, charged rod, positive
3. charged rod, neutral sphere, negative
4. charged rod, neutral sphere, positive

Q. Two spheres have radii 10 cm & 20 cm. One of the sphere is given 150 microcoulomb charge and connected by a wire. Their common potential will be- (1) 9 × 10^6 volts (2) 4.5 × 10^6 volts (3) 1.8 × 10^6 volts (4) 1.35 × 10^9 volts

Q.

What is forbidden energy gap?

Q.

Which is a better conductor - Aluminium or Copper?

Q.

Name two metals which are bad conductors of electricity.

Q. 74.Two uniformly charged non conducting hemispherical shells each having uniform charge density and radius R form a complete sphere ( not stuck together) and surround a concentric sperical conducting shell of radius R/2. If hemispherical parts are in equilibrium then minumum surface charge density of inner conducting shell is.

Q. Write any two distinguishing features between conductors, semiconductors and insulators on the basis of energy band diagrams.

Q.

$C,Si$, and $Ge$ have the same lattice structure. Why is $C$ insulator while $Si$ and $Ge$ intrinsic semiconductors?

Q. A pure semiconductor behaves like an insulator at -

1. $273\text{K}$
2. $0\text{K}$
3. $293\text{K}$
4. $300\text{K}$

Q. In a semiconductor, the concentration of electrons is $8\times {10}^{14}{\text{per cm}}^3$ and that of the holes is $5\times {10}^{12}{\text{per cm}}^3$. The semiconductor is

1. $P$-type
2. $N$-type
3. Intrinsic
4. $PNP$-type

Q. A sphere of radius R and charge Q is plaan imaginary sphere of radius 2R whose centrecoincides with the given sphere. The flux related toimaginary sphere isplaced inside(22Q4Q(3) E(4) E,

Q. 69.What is the potential inside a uniformly charged non conducting sphere? Click he

Q.

Cotton is a good conductor of electricity

1. True
2. False

Q.

Name any four insulators.

Q.

Which of the following is an example of a direct band gap intrinsic semiconductor?

1. Silicon

2. Germanium

3. Gallium Arsenide

4. All of these

Q. When a potential difference $\left(V\right)$ is applied across a conductor, the thermal speed of electrons is

1. Zero
2. proportional to $\sqrt{T}$
3. proportional to $\left(T\right)$
4. proportional to $V$

Q.

For an insulator, the forbidden energy gap is

1. $1MeV$

2. $0.1MeV$

3. $1eV$

4. $5eV$

Q. If band gap between lowest conduction band and highest valence band is greater than 3ev, then material is

1. Semiconductor
2. Conductor
3. Elastomer
4. Insulator

Q. Why doesnt fire or flame cast a shadow

Q. Electric field lines of force is ____ near isolated charged particle.

1. denser
2. rarer
3. denser for positive charge
4. rarer for negative charge.

Q.

The energy band gap is maximum in

1. Metals

2. superconductors

3. Insulators

4. Semiconductors

Q. If there is a cavity is present inside a uniformly charged sphere, why field inside cavity is uniform though there is no charge inside it & similarl in case of gravitational field though there no mass is present?

Q.

Wool is the conductor of electricity.

1. True
2. False