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Physics

Calculate the total resistance across AB:

Calculate the total resistance across AB. ICSE 2020 Physics Solved Question Paper.

Current Electricity

ICSE 2020

Answer

This circuit consists of two parts. In the first part, the resistances 3 ohm and 6 ohm are connected in parallel. If Rp is the equivalent resistance then

1Rp=13+161Rp=2+161Rp=361Rp=12Rp=2 Ω\dfrac{1}{Rp} = \dfrac{1}{3} + \dfrac{1}{6} \\[0.5em] \dfrac{1}{Rp} = \dfrac{2 + 1}{6} \\[0.5em] \dfrac{1}{Rp} = \dfrac{3}{6} \\[0.5em] \dfrac{1}{Rp} = \dfrac{1}{2} \\[0.5em] \Rightarrow R_p = 2 \space Ω

Therefore, Rp = 2 Ω

In the second part, Rp (i.e., 2 ohm) and 5 ohm are in series. If the equivalent resistance = Rs the we get,

Rs = 2 + 5 = 7 Ω

Hence, equivalent resistance across A and B = 7 Ω

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