## Can the frictional electricity produced during landing of a plane be used for constructive purposes?

As we know that in aeroplane during landing the charged produced in it due to the friction with ground are earthed through its wheels; can this charge be stored with the help of a capacitor and used for useful purpose?

I feel that this is a metter for research.

If you feel otherwise and know some method to tap this potential, please post.

## What does a rheostat control?

What does Rheostat controls? electron drift velocity or quantity of electrons?

We know I=nAve
I=current
n=quantity of electron
A=conductor area
e=electron charge
v=drift velocity

## Direction of magnetic field due to a current carrying conductor

“How do we know the direction of magnetic field around the current carrying conductor?” Asked Nikhil Incoming search terms:direction of magnetic field around a current carrying conductorDIRECTION OF MAGNETIC FIELD IN CURRENT CARRYING CONDUCTORmagne...

## Electrons and flow of electrons – Did you have this doubt before?

“When an electric cell is connected to a circuit, electrons flow away from the negative terminal in the circuit. But within the cell, electrons flow to the negative terminal. Explain? Answer: The question seems to be the result of some misconceptions. If we consider an electrochemical cell, it is the chemical reactions which develops and ...Read the full post

## Change in resistance due to stretching a wire

“There is a wire whose resistance is R. it is streched, and its length gets increased to 2%. find new resistance.” – Knishka Agrawal asked Answer: The resistivity does not change due to stretching, but the length and area of cross section changes; but the volume remains constant. Therefore, resistance changes which can be calculated ...Read the full post

## What is meant by charge on a capacitor?

Mohit asked this question:

“What is meant by charge on a capacitor?”

Answer: As we know, a simple capacitor (say a parallel plate capacitor) consists of two plates parallel to each other. When charged, charge on either plate of the capacitor is called charge on the capacitor.

The following links will help you explore further and understand more

## DERIVATION OF CELLS IN SERIES AND PARALLEL

jaipreet singh asked: “can you please tell me the DERIVATION OF CELLS IN SERIES AND PARALLEL?”

Answer: I am posting here the simplified treatment to calculate the current in a circuit with combination of cells.

In this derivation it is assumed that all cells have the same EMF and same internal resistance.

CELLS IN SERIES

Consider n identical cells of emf E and internal resistance r connected in series across an external resistor of resistance R.

The total internal resistance = nr (since the internal resistances come in series)

The total resistance in the circuit = nr+R

The total emf = nE (since the emfs add up in series circuit)

Therefore, the current in the circuit;$current =\frac{Total Emf}{Total resistance}$
$I=\frac{nE}{nr+R}$

PARALLEL COMBINATION OF CELLS

Consider m identical cells of emf E and internal resistance connected in parallel across an external resistor of resistance R.

The total emf in circuit = E (Since each cell has the same emf and they are in parallel)

The net internal resistance = r/m (since the cells are in parallel, their resistances are also in parallel. If m identical resistances are in parallel, the effective resistance is r/m)

The total resistance in circuit = R + r/m

Therefore, the current in circuit;$Current = \frac{Total EMF}{Total Resistance}$
$I = \frac{E}{mr+R}$

MIXED COMBINATION OF CELLS

Consider a combination of m rows of n cells each. The emf of each cell is E and the internal resistance of each cell is r. This combination is connected across and external resistance R.

The total EMF = nE

The net internal resistance = nr/m

The total resistance in circuit = R + nr/m

The current in circuit; $Current = \frac{Total EMF}{Total Resistance}$
$I = \frac{nE}{\frac{nr}{m}+R}=\frac{nmE}{nr+mR}$