The brightness of the lamp is proportional to the current flowing through the lamp: the larger the current, the brighter the lamp.
The current flowing through the lamp is given by Ohm's law:

where
V is the potential difference across the lamp, which is equal to the emf of the battery, and R is the resistance of the lamp.
The problem says that the battery is replaced with one with lower emf. Looking at the formula, this means that V decreases: if we want to keep the same brightness, we need to keep I constant, therefore we need to decrease R, the resistance of the lamp.
<u>Correct Question:</u>
Calculate the distance (in km) charlie runs if he maintains an average speed of 8 km/hr for 1 hour
<u>Answer:</u>
The total distance covered by Charlie is 8 km in 1 hour.
<u>Explanation:</u>
The average velocity as given in the question is,
v = 8 km/hr
Total time taken,

As we know the formula to evaluate the total distance d when the average velocity and time is given;




Hence, the total distance covered by Charlie in 1 hour will be 8 km.
Answer:
Anybody which is in state of rest ,will be in rest if we don't apply any external force ...
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