Question

a torch bulb is rated 2.5 v and 750 mA calculate its power, its resistance ,and energy consumed, if the bulb is lighted for 4 hours​

Answer 1

Answer:

Explanation:

Solution,

Here, we have

Voltage, (V) = 2.5 V

Current, (I) = 750 mA = 0.75 A

Here, the bulb is lighted for 4 hours.

(i) Power

Power generated = VI

Power generated = 2.50 × 0.75

Power generated = 1.87 W

Hence, the Power generated is 1.87 W.

(ii) Resistance

Resistance (R) = V/I

Resistance (R) = 2.5/0.75

Resistance (R) = 3.33 Ω

Hence, the Resistance is 3.33 Ω.

(ii) Energy consumed in 4 hours

Energy consumed = P × t

Energy consumed = 1.87 × 4

Energy consumed = 7.48 wh

Hence, the energy consumed in 4 hrs is 7.48 wh.

Answer 2

Given

➝ Potential difference = 2.5 v

➝ Current = 750 mA

To find

➝ Power of bulb

➝ Resistance of bulb

➝ Energy consumed if it it lighted for 4 hours.

Solution

Now we have ;

☛ Potential difference (V) = 2.5v

☛ Current (I) = 750 mA = (750)/1000 = 0.75 A

At first to find resistance we will use Ohm's law :

➝ V = I * R

➝ 2.5 = 0.75 * R

➝ R = 2.5/0.75

➝ R = 3.33Ω

∴ Resistance of bulb = 3.33Ω

_____________________________

Now we have ;

☛ Resistance (R) = 3.33Ω

☛ Potential difference (V) = 2.5v

Now we will use the formula :

➝ Power (P) = V²/R

➝ P = (2.5)²/3.33

➝ P = 6.25/3.33

➝ P = 1.87 W

∴ Power of bulb = 1.87 Watts.

____________________________

Now we have ;

☛ Power (P) = 1.87 W

☛ Time (t) = 4 hours.

Now we also know that,

➝ Power (P) = Energy (W)/Time(t)

➝ 1.87 = W/4

➝ W = 1.87 × 4

➝ W = 7.48 Joules.

∴ Energy consumed by bulb = 7.48 J