Tag: electric force

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Questions Related to electric force

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

Two copper spheres, $A$ and $B$, are identical in all respect but A carries a charge of $-3 \mu C$ whereas $B$ Is charged to $+1 \mu C$. The two spheres are brought together until they touch and then separated by some distance. Which of the following statements is true concerning the electrostatic force $F$ between the spheres?

  1. $F = 0$ as one of the spheres is uncharged

  2. $F = 0$ as both the spheres are uncharged

  3. $F$ is attractive

  4. $F$ is repulsive.
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Charge on $A^{+}$ sphere $=-3$ $uC$

Charge on $B$ sphere $=+1$ $uC$
When they are connected the charge get redistributed, i.e.
$\Rightarrow$ Charge on both sphere $=\dfrac{-3+1}{2}$ $uC=-1$ $uC$
So charge on either sphere $=-1$ $uC$
Therefore, After connecting charge on sphere $A=-1$ $uC$
After connecting charge on sphere $B=-1$ $uC$
Therefore, there will be a repulsive force between the sphere because of like charges.

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

The potential at a point $(x, 0, 0)$ is given by $V = \left(\dfrac{1000}{x} + \dfrac{1500}{x^2} + \dfrac{500}{x^3}\right)$. The intensity of the electric field at $x = 1$ will be

  1. $550 V/m$

  2. $55 V/m$

  3. $55000 V/m$

  4. $5500 V/m$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation
$V=(\cfrac{1000}{x}+\cfrac{1500}{x^{2}}+\cfrac{500}{x^{3}})$
We know that, $E=\cfrac{-dv}{dr}$
So,
$E=\cfrac{-d(\cfrac{1000}{x}+\cfrac{1500}{x^{2}}+\cfrac{500}{x^{3}})}{dx}$   at $x=1$
$=-[\cfrac{(-1000)}{x^{2}}-\cfrac{2\times 1500}{x^{3}}-\cfrac{3\times 500}{x^{4}}] _{x=1}$
$=1000+3000+1500=5500\,V/m$
Multiple choice physics electric fields introduction to electrostatic force electric force charging and discharging

Five ball numbered $1$ to $5$ are suspended using separate threads. Pairs $(1,2)$, $(2,4)$ and $(4,1)$ show electrostatic attraction while pairs $(2,3)$, $(4,5)$ show repulsion. Therefore, ball $1$ must be

  1. neutral

  2. metallic

  3. positively charged

  4. negatively charged
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Attraction between 1 and 2, 2 and 4, and 4 and 1 implies that 1, 2, and 4 must have different charges or one is neutral. Repulsion between 2 and 3, and 4 and 5, implies 2 and 3 have the same charge, and 4 and 5 have the same charge. If 1 is neutral, it attracts both positive and negative charges, which is consistent with the observations.

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

If a comb is rubbed on dry hairs, and then brought near paper pieces, it :

  1. attracts paper

  2. repels paper

  3. remains indifferent to paper

  4. either attracts or repels paper
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

If we bring small bits of paper near a rubber (or plastic) comb, it is found that the comb does not attract the bits of paper. But if the same comb is first rubbed on dry hairs and then it is brought near the paper pieces, it attracts them.

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

True or False?
S1: Similar charge attracts each other.
S2: Similar charge repels each other.

  1. True, True

  2. True, false

  3. False, True

  4. false, false
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

There are 2 types of electrical charges - positive and negative - are said to be opposite types of charge. Consistent with our fundamental principle of charge interaction, a positively charged object will attract a negatively charged object. Oppositely charged objects will exert an attractive influence upon each other. In contrast to the attractive force between two objects with opposite chargess, two objects that are of like charge will repel each other. That is, a positively charged object will exert a repulsive force upon a second positively charged object. This repulsive force will push the two objects apart. Similarly, a negatively charged object will exert a repulsive force upon a second negatively charged object. Objects with like charge repel each other.
Hence, the statement is false.