To practice problem-solving strategy 25.1 power and energy in circuits. a device for heating a cup of water in a car connects to the car's battery, which has an emf e = 10.0 v and an internal resistance rint = 0.03 ω . the heating element that is immersed in the cup of water is a resistive coil with resistance r. david wants to experiment with the device, so he connects an ammeter into the circuit and measures 10.5 a when the device is connected to the car's battery. from this, he calculates the time to boil a cup of water using the device. if the energy required is 100 kj , how long does it take to boil a cup of water?