The discussion revolves around finding the electric potentials at points P, Q, and R in a circuit where point S is earthed. The context involves applying Kirchhoff's laws and understanding voltage drops across resistors in relation to the circuit's configuration.
Some participants have provided guidance on using Ohm's law to calculate voltage drops and have encouraged further exploration of the problem. There is an acknowledgment of the need to consider the reference point for potential measurements, and attempts to clarify the connections between current flow and potential differences are ongoing.
Participants are working under the constraints of a homework assignment, which may limit the information they can share or the methods they can use. The discussion reflects a mix of understanding and uncertainty regarding the application of circuit laws and the implications for potential at specific points.
Doc Al said:You found the current. In what direction does it flow? Use that to find the voltage drops across each resistor.
Good.thereddevils said:ok , the current is flowing in the clockwise direction .
Sure. The voltage across each resistor is given by Ohm's law: ΔV = IR. To find the sign of the voltage across the resistor, you need to know the direction of the current. Hint: Does current across a resistor flow from lower to higher potential or from higher to lower?Could you elaborate a little further on the voltage calculation of each resistors ?
To find the potential at any point with respect to some reference, just add up the voltage drops across each piece. Here your reference is point S, which is marked as ground and thus is at 0 Volts. To find the potential of point P, for example, you need to find ΔV from S to P. S to P contains a battery, so what's ΔV? To find the potential of point Q, you'll add up the voltage drops across S-P and P-Q. What's the voltage drop from P to Q across that 2 Ω resistor?But the question is asking for the potential at points P,Q and R respectively . How is it related to the potential difference across the resistors .
Doc Al said:Good.
Sure. The voltage across each resistor is given by Ohm's law: ΔV = IR. To find the sign of the voltage across the resistor, you need to know the direction of the current. Hint: Does current across a resistor flow from lower to higher potential or from higher to lower?
To find the potential at any point with respect to some reference, just add up the voltage drops across each piece. Here your reference is point S, which is marked as ground and thus is at 0 Volts. To find the potential of point P, for example, you need to find ΔV from S to P. S to P contains a battery, so what's ΔV? To find the potential of point Q, you'll add up the voltage drops across S-P and P-Q. What's the voltage drop from P to Q across that 2 Ω resistor?
Doc Al said:Perfecto!
Just for fun, realize that you can find the potential of a point (Q, say) by starting from S and going clockwise around the circuit or by going counter-clockwise. Do it both ways and check that you get the same answer.