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"Battery Ba is connected in series with resistor Ra = 2Ω. Battery Bb is connected in series with resistor Rb = 4Ω. Battery Ba has a voltage of 2V and inner resistance of 1Ω. Bb has a voltage of 1V and inner resistance of 2Ω. The two circuits are connected in parallell in a way that the polarity on Bb is switched (+ on Ba is connected to - on Bb). What is the current flowing through Bb and voltage drop of Rb?"

First of all I have a bit of trouble to sketch the circuit. This is my attempt (not sure if it's correct) enter image description here

If it's correct. My attempt was to do node analysis on the upper (three-way node). But I'm not sure on how to take into account the inner resistance of the batteries when calculating.

Could this be the correct interpretation of the problem? enter image description here

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  • \$\begingroup\$ We need you to be accurate in your diagram. \$\endgroup\$
    – Andy aka
    Mar 29 at 16:15
  • \$\begingroup\$ I wasnt sure on how to draw the battery using a schematic tool \$\endgroup\$
    – Gripen
    Mar 29 at 16:22
  • \$\begingroup\$ Use EveryCircuit or similar software (this one has an online version), sketch it there and you'll see "the electrons" flowing, the voltage, amperage and everything you need and don't need to know. \$\endgroup\$
    – Fusseldieb
    Mar 29 at 16:35
  • \$\begingroup\$ Did my best, hopefully that circuit is better to understand \$\endgroup\$
    – Gripen
    Mar 29 at 16:45
  • 1
    \$\begingroup\$ I don't think you want the wire from the top horizontal line, around the circuit to Ground. \$\endgroup\$ Mar 29 at 16:50

1 Answer 1

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Let's do it step-by step:

  1. Battery Ba is connected in series with resistor Ra = 2Ω.

  2. Battery Bb is connected in series with resistor Rb = 4Ω.

schematic

simulate this circuit – Schematic created using CircuitLab

  1. Battery Ba has a voltage of 2V and inner resistance of 1Ω.

  2. Bb has a voltage of 1V and inner resistance of 2Ω.

schematic

simulate this circuit

  1. The two circuits are connected in parallell in a way that the polarity on Bb is switched (+ on Ba is connected to - on Bb).

schematic

simulate this circuit

The location of the 0V reference node is arbitrary. I've put it inside the schematic just so I wouldn't need to enlarge the box the schematic is in :)

What is the current flowing through Bb and voltage drop of Rb?

Hint: how would you connect two AA batteries to obtain 3V?

You can do DC simulation on the schematic above and check your answers and intuition, by the way!

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