"several light bulbs each of resistance 1.25 ω are connected in series across a 115 v power supply. if the current through the circuit is 2 a, what is the number of light bulbs in the circuit?

The number of bulbs = 46 bulbs

Explanation:

Ohm's Law: Ohm's law states that the current flowing through a conductor is directly proportional to its potential difference across its ends. At constant temperature and pressure. It can be expressed mathematically as

V = IR Equation 1

making R the subject of formula in equation 1

R = V/I Equation 2

Where R = combined resistance of the several bulbs, V = potential difference, I = current through the circuit.

Given: V= 115 V. I = 2 A.

Substituting these values into equation 2,

R = 115/2

R = 57.5 Ω

Since the bulbs are connected in series,

Number of bulbs = combined resistance/resistance of each bulb

Number of bulbs =  R/Rₙ Equation 3

Where Rₙ = resistance of each bulb, R =combined resistance of the bulb.

Also given: Rₙ = 1.25 Ω, and R = 57.5 Ω

Substituting these values into equation 3

Number of bulbs = 57.5/1.25

Number of bulbs = 46 bulbs.

Therefore the number of bulbs = 46 bulbs

because growing process had stoped after 4-5 year

the minimum constant speed at which she can catch the train is 2.7 m/s

given:

acceleration = 0.6

time = 4.5 s

to find:

velocity = ?

formula used:

from 1st kinematic equation we get,

v = u + at

u = initial speed of train = 0 m/s

v = final speed of the train

a = acceleration of the train

t = time

solution:

from 1st kinematic equation we get,

v = u + at

u = initial speed of train = 0 m/s

v = final speed of the train

a = acceleration of the train

t = time

v = 0 + (0.6 × 4.5)

v = 2.7 m/s

the minimum constant speed at which she can catch the train is 2.7 m/s