Why does the ground have more voltage drop across than the cabels connecting the metal poles together? I could not wrap my head around this. All I could assume is that current stays constant, therefore, the voltage drop must increase when there is higher resistance to maintain the same current throughout the circuit. Is this right? If so, I still don't get why. Why does it have to maintain the same current? I thought current was the dependent variable in simple circuit.
The current in the circuit loop is indeed constant. It must be because no electrons are lost and current is just the movement of electrons.
Indeed ground is not a good conductor, actually it is a bad conductor. This results in more voltage drop for the same current compared to a more conductive (less resistance) wire. This is described by Ohm's Law.
The current indeed depends on the circuit. The current is determined by the voltage V and the total resistance R. Then Ohm's Law states: $$I = V / R$$ where I is the current. So a smaller R (less resistance) results in more current.
A few basics:
- The source voltage remains fairly constant, 2400 V, in this scenario. The electricity grid is designed on the basis that voltage is constant +/-10% throughout and that guarantees reasonably steady voltage in your home, etc.
- The current varies depending on the load. This stands to reason: a small lamp will draw a small current because its resistance (to current) is high. A big heater will draw a large current because its resistance is low.
Why does the ground have more voltage drop across than the cables connecting the metal poles together?
- The answer is that, if the voltages marked on the drawing are correct, the ground resistance must be higher. Let's guess that the cable resistance from the source to the break is 1 Ω. Since the voltage drop across the ground is 239 times the 10 V drop along the wire then the ground circuit must be 239 Ω. This will be made up of the resistance of the contact of the wire with the ground, the ground resistance itself and the earth connection at the source.
- The cables don't connect the poles together. The cables are insulated from the poles which are there only for support.
All I could assume is that current stays constant, therefore, the voltage drop must increase when there is higher resistance to maintain the same current throughout the circuit. Is this right?
- No, the voltage remains constant. Current varies with the resistance / load.
I thought current was the dependent variable in simple circuit.
- Yes, this is correct. The current varies with the load.