Answer:

Explanation:
To solve the problem, the concepts related to the magnetic field and the current produced in a lightning bolt are necessary.
The current is defined by the load due to time, that is to say

Where,


So the current can be expressed as:


Once the current is found it is now possible to find the magnetic field, as this is given by the equation,

Where,
Permeability Constant
I= Current
r= radius
Replacing the values we have


Explanation :
A power amplifier is used to amplify electric signals i.e. to increase the low power signal to higher powers.
A PNP transistor is connected in a circuit so that the collector-base junction remains reverse biased and the emitter-base junction is forward biased.
This transistor can be used as a power amplifier because it gives a much larger output current. The gain of an amplifier shows the amount of amplification. It is the difference between the input and the output signals.
Answer:
Explanation:
We shall apply Stefan's formula
E = AσT⁴
When T = 300
I₁ = Aσ x 300⁴
When T = 400K
I₂ = Aσ x 400⁴
I₂ / I₁ = 400⁴ / 300⁴
= 256 / 81
= 3.16
I₂ = 3.16 I₁ .
To solve this problem we will apply the concepts related to the Electrostatic Force given by Coulomb's law. This force can be mathematically described as

Here
k = Coulomb's Constant
Charge of each object
d = Distance
Our values are given as,


d = 1 m
a) The electric force on charge
is


Force is positive i.e. repulsive
b) As the force exerted on
will be equal to that act on
,


Force is positive i.e. repulsive
c) If
, a negative sign will be introduced into the expression above i.e.


Force is negative i.e. attractive
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