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Grade 12Electric Current

A storage battery of emf 12V and internal resistance 0.5 ohm, is to be charged by a 120V D.C supply of negligible internal resistance. What resistance is required in the circuit for the charging current to be 3A?
Calculate:
i)How much chemical energy from the dc source is converted to electrical energy?
ii)How much electrical energy is converted to chemical energy in the storage battery?

Abdul Jawwad

6 Years agoGrade 12

2 Answers

Arun

Approved Tutor Answer6 Years ago

By applying Kirchoff's voltage law , we get, 3R + 12 + (3×0.5) = 120

From abov eqn., we get R = 35.5 Ω

If t is charging time in seconds, electrical energy converted into chemical energy in storage battery = ( 12 × 3 × t ) J = 36t J

If t is charging time in seconds, chemical energy converted into electrical energy in dc source = ( 120 × 3 × t ) J = 360t J

Vikas TU

6 Years ago

Dear student

The Resistance value is incorrect

Applying Kirchoff voltage rule we get
net emf = (120-12)=117 V , net resistance =( R+r) and net current =3A
now 117=i xRnet
117/3 =r+R
39-0.5 =R=38.5 Ω

Hope this will help

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