## BdPhO Regional (Dhaka-South) Secondary 2019/1

Discuss Physics and Physics Olympiad related problems here
SINAN EXPERT
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### BdPhO Regional (Dhaka-South) Secondary 2019/1

BdPhO Regional (Dhaka-South) Secondary 2019(1).png (13.87 KiB) Viewed 1572 times

What will be the reading on the voltmeter?
(See the figure)

চিত্রে ভোল্টমিটারে পাঠ কত দেখাবে?
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SINAN EXPERT
Posts: 38
Joined: Sat Jan 19, 2019 3:35 pm
Contact:

### Re: BdPhO Regional (Dhaka-South) Secondary 2019/1

Firstly let's make the picture easy.
BdPhO Regional (Dhaka-South) Secondary 2019(1S).png (14.32 KiB) Viewed 1518 times
Here, \$R_1=2 Ω, R_2=3 Ω, R_3=1 Ω, R_4=4 Ω, R_5=5 Ω\$
Current cannot flow throw voltmeter, so \$R_5\$ is useless.
Equivalent Resistance, \$R=\dfrac{(R_1+R_2)(R_3+R_4)}{R_1+R_2+R_3+R_4}=2.5Ω\$
\$∴\$ \$I=\dfrac{V}{R}=4\$ \$A\$
Now, \$I_1=\dfrac{V_{ab}}{R_1+R_2}=\dfrac{IR}{R_1+R_2}=2\$ \$A=I_3\$
Hence, \$V_a-V_{1,2}=I_1R_1=4\$ \$V\$, \$V_a-V_{3,4}=I_3R_3=2\$ \$V\$
\$∴\$ \$V_{3,4}-V_{1,2}=V=2\$ \$V\$
\$The\$ \$only\$ \$way\$ \$to\$ \$learn\$ \$mathematics\$ \$is\$ \$to\$ \$do\$ \$mathematics\$. \$-\$ \$PAUL\$ \$HALMOS\$