A battery can create a #8 V# emf across its terminals. If this battery powers a circuit that requires #1.7# amps for #4# minutes, how much chemical energy is lost by the battery during this time?

1 Answer
Douglas K.
Apr 18, 2018

An equation for energy consumed is:

#"Energy" = "Power" xx "Time [1]"#

One of the equation for electric power consumed is:

#"Power" = "Voltage" xx "Current [2]"#

Substitute equation [2] into equation [1] to find an equation for electrical energy consumed by the circuit:

#"Energy" = "Voltage" xx "Current" xx "Time"#

We must be careful to use a consistent set of units; one such set of units is where the unit Joules is defined as #V*A*s#, therefore, we must convert the given time from minutes to seconds:

#4" min" to 240" s"#

#"Energy" = 8" V" xx 1.7" A" xx 240 " s"#

#"Energy" = 3260" Joules"#

NOTE: This assumes that the battery is #100%# efficient.

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