Question

Determine the resistance of an electric appliance which takes a current of 12 A from A 240 V source. Find also the power rating of the appliance and energy used in 20 hr.

Answer 1

Explanation:

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Answer 2

Answer:

$\bigstar{\bold{Resistance=20\: \Omega}}$

$\bigstar{\bold{Energy\:used=207360\:kJ}}$

$\bigstar{\bold{Power=2880\:W}}$

Explanation:

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

• Current (I) = 12 A
• Voltage (V) = 240 V
• Time taken = 20 hr = 72000 s

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

• Resistance

• Power
• Energy

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

Resistance:

→ By Ohm's law we know that,

  R = V/I

→ Substituting the datas, we get the value of resistance

  R = 240/12

  R = 20 Ω

→ Hence resistance of the conductor is 20 Ω

$\boxed{\bold{Resistance=20\: \Omega}}$

Energy:

→ By Joule's law we know that,

  H = I² R t

→ Substituting the datas, we get the value of energy

  H = 12 × 12 × 20 × 72000

  H = 144 × 1440000

  H = 207360000 J = 207360 kJ

→ Hence energy used by the appliance = 207360 kJ

$\boxed{\bold{Energy\:used=207360\:kJ}}$

Power:

→ We know that power is given by the equation.

  P = V I

→ Substituting the datas we get the value of power

  P = 240 × 12

  P = 2880 W

→ Hence the power of the appliance is 2880 W

$\boxed{\bold{Power=2880\:W}}$

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

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

V = R I

→ Joule's law state that the heat dissipated in a conductor is directly proportional to the square of the current flowing through it, resistance and time for which current flows through the conductor.

H = I² R t