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The electric current through a wire varies with time as I=I0+ t, where I0=20 A and =3 A/s. The amount of electric charge crossed through a section of the wire in 20 s is :
(3) 1000 C
I= dqdt q= 020(20+3t) dt
= [20t+ 3t22 ]020
=400+600=1000 C
Shortcut: I is linear in t ⇒ q=Iavg t= 20+802 20=1000 C
Answer: (3)
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