Question

A wire was connected to a 1.5 volt cell and had a 1.2 ampere of current passing through it. what is the resistance of the wire ?

Answer 1

Answer:

Correct option is

B

1.47 V

Given that,

Current = 0.2 A

Internal resistance = 0.15 ohm

e. m. f = 1.5 volt

We know that,

V=E−ir

V=1.5−0.2×0.15

V=1.5−0.03

V=1.47volt

Hence, the potential difference is 1.47 V across both the ends of the cell

Explanation:

follow

Answer 2

Answer:

If the 1.5 volt battery is connected to a cable. The resistance of the wire is very small, then from ohm's law the current should be very high. How is this possible? Is there any missing term in the calculation?

In short the answer is Internal resistance.

A battery or cell is not just a source or voltage but it also has resistance. This is due to the structure of the battery which inhibits an infinite current flow hence has resistance.

Here E= voltage that is 1.5V

R = external resistance that is the wire

r = internal resistance

Hence the current I = E / (R + r)

even if the wire has negligible resistance that is R ~ 0. Still the maximum current will be I = E/r which is finite.

For atypical AA battery is of order 0.1 Ohms. Therefore the maximum current (considering wire resistance to be zero) cannot be more th

If a cable is connected to a 1.5volt battery for the short circuit, a large but finite current flows in the cable. If the emf of the battery and its internal resistance are ‘E’ and ‘r’ respectively; then potential difference ‘V’across the cable resistance ‘R’ is

V=E-ir. (Here, I=E/(r+R))

=E-rE/(r+R))

=E R/(r+R)

=E/(1+(r/R))

In case when the cable resistance ‘R’becomes very small may be zero (think of resistance of superconductors), the potential difference ‘V’ becomes zero as

V=E/(1+infinite value) =0

(since, r/R is infinite)

So the power obtained is zero(P=Vi=0).Current is not zero and it is E/r).The internal resistance ‘r’ of the battery, can not be zero due to the resistance of its electrolytic solution.Thus, although the current flow in the circuit may be very high, but the power obtained can't be high ; it is zero.

Explanation:

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