[SPM Physics Electric question] Why the voltmeter reading is same for both diagram?


Rajah 38 dan Rajah 39 menunjukkan dua litar elektrik. Ammeter, voltmeter dan sel kering adalah sama bagi kedua-dua rajah.
Diagram 38 and Diagram 39 show two electric circuit. Ammeter, voltmeter, and dry cells are identical in both diagrams.


Hi Farhaini,
The voltage across the conductor is given by V=IR
In both diagrams, the voltage is the same because the number of batteries are the same, so the same amount of voltage is supplied by the batteries.
We assume that wires usually have 0 resistance to make things simple, so we have the same voltage across the conductor. (I think the question should also mention that the internal resistance of the battery is 0 to avoid confusion :sweat_smile:)

Iā€™m not sure if you have come across this formula, R=\frac{\rho l}{A}, where \rho is the resistivity, l is the length, A is the area. You can see that R \propto l.

In both diagrams, we can see that the length is different. Diagram 38 has a smaller length, so smaller resistance. Since voltage is fixed, then that would mean Diagram 38 has a larger current. Diagram 39 has a greater length, so greater resistance, and smaller current.

Hope this helps! :slight_smile:

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Thankyou very muchh :relaxed::relaxed::+1::+1:

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