Tag: charging and discharging

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

In the thunderstorm, the charges accumulate near the upper edges of clouds are

  1. negatively charged

  2. positively charged

  3. neutral

  4. none of these
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

We have to find the nature of charges on upper edges of clouds in a thunderstorm, the air currents move upwards while the water droplets move downward. This vigorous movement causes separation of charges. This leads to the positive charges collected near the upper edges of clouds and the negative charges to accumulate near the lower edges of the clouds.

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

Charge 1 attracts Charge 2, Charge 2 repels Charge 3, and Charge 3 attracts Charge 4. Which of the following option must hold good for the given condition of four point charges? 

  1. Charge 1 attracts Charge 4

  2. Charge 2 attracts Charge 3

  3. Charge 1 repels Charge 3

  4. Charge 2 repels Charge 4

  5. Charge 1 repels Charge 4
Reveal answer Fill a bubble to check yourself
E Correct answer
Explanation

If charge 1 is positive and charge 2 is negative, then charge 1 and 2  will attract. As charge 2 and 3 repels so charge 3 should be negative. Since charge 3 and 4 attracts so charge 4 should be positive. Thus, charge 1 and 4 both are same charge so they will repel. If you take charge 1 is negative and 2 is positive similarly you get 4 is negative so 1 and 4 both have same charge. 


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.