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I have summarised my understanding of electric potential energy and its role in simple circuits below. This is already more detailed than my course requires, but I have learnt it as I find it helpful in understanding the rest of the course. The section in bold is the main bit that I'm unsure about. Is it accurate to say that potential energy is converted to heat energy in this way?

Internal Circuit

The battery moves positive charge from the cathode to the anode. This is against the direction of the electric field, so it requires energy. The battery uses chemical energy to give electric potential energy to the charges. For example, a $12 \ \mathrm{V}$ battery provides a $1 \ \mathrm{C}$ charge with $12 \ \mathrm{J}$ of electric potential energy.

External Circuit

The charge at the anode is attracted by the electric field and moves through the circuit towards the cathode. As it moves, its electric potential energy is converted to heat energy as it collides with the particles in the conductor. Its kinetic energy, referring to its drift velocity, remains constant. When it reaches the cathode, it has no electric potential energy. This is why the neutral wire in mains electricity is at $0 \ \mathrm{V}$; all the potential energy has been supplied to the appliances in the house.

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  • $\begingroup$ Perhaps you can tell us what aspect about the bold faced that "concerns" you $\endgroup$ – Bob D Apr 29 at 14:30
  • $\begingroup$ @BobD Is that really how potential energy is converted to heat energy? I can't see any problem with it myself, but it's an assumption that I have made, rather than one I've been taught. I just want to be 100% sure before I write in in an exam, if you know what I mean. $\endgroup$ – Evan Apr 29 at 14:53
  • $\begingroup$ OK. I've posted an answer. Hope it helps. $\endgroup$ – Bob D Apr 29 at 15:27
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As it moves, its electric potential energy is converted to heat energy as it collides with the particles in the conductor. Its kinetic energy, referring to its drift velocity, remains constant.

Just to be clear, the conversion of electrical potential energy to heat energy only applies to the resistance in the circuit. The electrical potential energy can also be used to charge capacitors in which case the energy supplied by the voltage source is stored as electrical potential energy in the electric field of the capacitor. Electrical potential energy can also be stored in the magnetic field of inductors.

That being said, your understanding of how electrical potential energy is converted to heat energy in the case of circuit resistance is basically correct. A rough mechanical friction analogy is the sliding of an object at constant velocity down an incline plane with friction. The moving object is an analogous to the moving charge. The constant velocity of the object is analogous to the constant drift current of the charge. The incline plane with friction is analogous to electrical resistance. The heat generated by mechanical friction on the incline plane is analogous to the dissipation of heat in the resistor. And finally the loss of gravitational potential energy of the block as it slides down is analogous to the loss of electrical potential energy.

Hope this helps

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  • $\begingroup$ Electric potential energy can be used in many other ways: driving electric motors, powering florescent or solid state light sources, or powering complex devices such as microwave ovens, tv's or computers. $\endgroup$ – R.W. Bird Apr 30 at 18:52

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