Question

A torch bulb is rated 2.5 V and 750 mA. Calculate (i) Its power (ii) its resistance and (iii) the energy consumed in 4 hours.

Answer 1

Answer:

PLEASE REFER TO THE ANSWER GIVEN BELOW

Explanation:

Given :

V=2.5 V

I=750mA= 750x10⁻³A

power =p=?

Power =V*I            

 =2.5x750x10⁻³

=1.875W

reistance :

V=IR

R=V/I=2.5/750x10⁻³=3.3 ohms

Energy consumed if bulb is lighted for 4 hours :

E=p*t=1.875x4=7.500Wh=27x 10³ joules

Answer 2

Answer:

$\bigstar{\bold{Power=1.875\:Watt}}$

$\bigstar{\bold{Resistance=3.33\: \Omega}}$

$\bigstar{\bold{Energy=27000\:J}}$

Explanation:

$\Large{\underline{\underline{\it{Given:}}}}$

• Potential difference (V)= 2.5 V
• Current = 750 mA = 0.75 A
• Time = 4 hr = 14400 s

$\Large{\underline{\underline{\it{To\:Find:}}}}$

• Power (P)
• Resistance (R)
• Energy (E)

$\Large{\underline{\underline{\it{Solution:}}}}$

Power:

→ Power is given by the formula

  Power = Potential difference × Current

  Power = 2.5 × 0.75

  Power = 1.875 W

$\boxed{\bold{Power=1.875\:Watt}}$

Resistance:

→ By Ohm's law resistance is given by

→ R = V/I

→ Substituting the datas we get,

  R = 2.5 / 0.75

  R = 3.33 Ω

$\boxed{\bold{Resistance=3.33\: \Omega}}$

Energy:

→ Energy is given by the formula,

 Energy = Power × Time

  Energy = 1.875 × 14400

  Energy = 27000 J

$\boxed{\bold{Energy=27000\:J}}$

$\Large{\underline{\underline{\it{Notes:}}}}$

→ Ohm's law state that the current flowing through a conductor is directly proportional to potential difference applied across its ends provided thatthe temperature and other physical conditions remain unchanged.

V = R I