Tag: charging and discharging

Questions Related to charging and discharging

An electric filament bulb can be worked from

physics electric fields introduction to electrostatic force electric force charging and discharging

  1. DC supply only

  2. AC supply only

  3. Battery supply only

  4. All above

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Correct Option: D
Explanation:

An electric filament bulb can be worked from

1. AC Current.
2. DC Current.
3. Battery current.

Option D is correct.

The filament of an electric bulb is made of :

physics electric fields introduction to electrostatic force electric force charging and discharging

  1. Carbon

  2. Aluminium

  3. Tungsten

  4. Nickel

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Correct Option: C
Explanation:

The filament of an electric bulb is made of tungsten because it has some amazing properties including the highest melting point $(3422^oC )$, lowest vapor pressure, and greatest tensile strength out of all the metals. Because of these It can reach high temperature before melting.  

Which is the best conductor of electricity?

physics electric fields introduction to electrostatic force electric force charging and discharging

  1. Iron

  2. Silver

  3. Copper

  4. Carbon

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Correct Option: B
Explanation:

Silver is a best conductor of electricity because it contains maximum number of free electron.Also the resistance of silver is very low.


Option B is correct.

True Or False?
1)A proton repels an electron.
2)An electron repels a proton.

physics electric fields introduction to electrostatic force electric force charging and discharging

  1. False, False

  2. True, True

  3. True, False

  4. False, True.

Show answer
Correct Option: A
Explanation:

The above statement is false. Unlike charges attract each other. A proton attracts an electron.

Like charges .......... and unlike charges.................

physics electric fields introduction to electrostatic force electric force charging and discharging

  1. Repel, Attract

  2. Attract, Repel

  3. Always attract

  4. Always repel

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Correct Option: A
Explanation:

There are two types of charges, positive and negative. Same type of charges (two positive or two negative) repel each other, while unlike charges (one positive and one negative) attract each other.

Like charges ____________  each other and unlike charges ____________ each other :

physics electric fields introduction to electrostatic force electric force charging and discharging

  1. repel, attract

  2. attract, repel

  3. repel, repel

  4. attract, attract

Show answer
Correct Option: A
Explanation:

The like charges repel and unlike charges attract each other, hence option A is correct answer.

An insulated conductor initially free from charge is charged by repeated contacts with a plate which after each contact is replenished to a charge $Q$ from an electrophorus. If $q$ is the charge on the conductor after the first operation,  The maximum charge which can be given to the conductor in this way is $Qq/(Q - q)$.

physics electric fields introduction to electrostatic force electric force charging and discharging

  1. True

  2. False

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Correct Option: A

 A point charge Q is placed at origin O. Let $\overrightarrow {{E _A}} $,$\overrightarrow {{E _B}} $ and $\overrightarrow {{E _C}} $ represent electric fields at A, B and C respectively. If coordination of A,B and C are respectively (1,2,3) m,(1,1,-1) m and (2,2,2) m  then 

physics electric fields introduction to electrostatic force electric force charging and discharging

  1. $\overrightarrow {{E _A}} \bot \overrightarrow {{E _B}} $

  2. $\overrightarrow {{E _A}} \parallel \overrightarrow {{E _B}} $

  3. $\left| {\overrightarrow {{E _B}} } \right|\parallel 4\left| {\overrightarrow {{E _C}} } \right|$

  4. $\left| {\overrightarrow {{E _B}} } \right|\parallel 8\left| {\overrightarrow {{E _C}} } \right|$

Show answer
Correct Option: C
Explanation:

$\overrightarrow{E _a}=\cfrac{h _E}{ra^3}=\cfrac{h _E}{1^2+2^2+3^2}(1\hat{i}+2\hat{j}+3\hat{k})\ \overrightarrow{E _a}=\cfrac{h _E}{14^{3/2}}(1\hat{i}+2\hat{j}+3\hat{k})\ \overrightarrow{E _b}=\cfrac{ha}{r _b^2}\overrightarrow{r _b}=\cfrac{h _E}{(1^2+1^2+1^2)}^{3/2}(1\hat{i}-1\hat{j}+1\hat{k})\=\cfrac{h _E}{3^{3/2}}(1\hat{i}-1\hat{j}+1\hat{k})\ \overrightarrow{E _c}=\cfrac{h _E}{r _c^2}\overrightarrow{r _c}=\cfrac{h _E}{(2^2+2^2+2^2)^{3/2}}(2\hat{i}+2\hat{j}+2\hat{k})$

$\quad=\cfrac{h _E}{12^{3/2}}(2\hat{i}+2\hat{j}+2\hat{k})$
Now 
$\overrightarrow{E _a}.\overrightarrow{E _b}=\cfrac{h _E}{14^{3/2}}(1\hat{i}+2\hat{j}+3\hat{k})=\cfrac{h _E}{3^{3/2}}(1\hat{i}-1\hat{j}+1\hat{k})\ \Rightarrow \overrightarrow{E _a}.\overrightarrow{E _b}=(\cfrac{h _E}{14^{3/2}})(\cfrac{h _E}{3^{3/2}})(1-2+3)\neq0$
Thus$\overrightarrow{E _a}$ and $\overrightarrow{E _b}$ are perpendicular to each other
$|E _c|=\cfrac{h _E}{12^{3/2}}(2^2+2^2+2^2)^{1/2}=\cfrac{h _E}{12^{3/2}}(12)^{1/2}\ \Rightarrow |\overrightarrow{E _c}|=\cfrac{h _E}{12}\ \overrightarrow|E _b|=\cfrac{ha}{3^{3/2}}(1^2+1^2+1^2)^{1/2}=\cfrac{ _E}{3}=4\times\cfrac{h _E}{12}=4|\overrightarrow{E _c}|$
So, $|\overrightarrow{E _b}|=4|E _c|$



Objects with the same type of charges attract each other.

physics electric fields introduction to electrostatic force electric force charging and discharging

  1. True

  2. False

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Correct Option: B
Explanation:

Object with same nature of charges repel each other i.e, positive charges repel positive charge and negative charges repel negative charge.

   And charges with opposite nature attract each other that is negative and positive charge attract each other.

Given statement is $False$.

To construct an air filled capacitor which can store $ 12 \mu C $ of charge, What can be the minimum plate area of the capacitor? (Dielectric strength of air is $3\times 10^6 V/m$ )

physics electric fields introduction to electrostatic force electric force charging and discharging

  1. $0.25 m^2$

  2. $0.45 m^2$

  3. $4.5 m^2$

  4. $0.35 m^2$

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Correct Option: C