# physics

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Your car's 31.5 W headlight and 2.15 kW starter are ordinarily connected in parallel in a 12.0 V system. What power would one headlight and the starter consume if connected in series to a 12.0 V battery? (Neglect any other resistance in the circuit and any change in resistance in the two devices. Answer to the nearest 0.1 W.)

• physics -

figure the resistance of each first R=power/12

then in series, add the resistances, and then power=12^2/Rt

This is acually ignoring a lot of characteristics of motors, as in the motor, effective resistance is not a constant, but depends on the voltage applied, and how fast the motor is turning and developing back EMF. But ignore all this for now.

• physics -

im still not getting it.

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