**Q11) [JEE main/AIEEE 2013] **

A charge Q is uniformly distributed over a long rod AB of length L as shown in the figure. The electric potential at the point O lying at distance L from the end A is:

* Answer to Q11:* The video solution is given in this video. Click to watch it.

**Q12) [ JEE MAIN/AIEEE 2010]**

A thin semi-circular ring of radius r has a positive charge distributed uniformly over it. The net field E at the centre is:

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*Q13) [ JEE main/AIEEE 2008] *

A parallel plate capacitor with air between the plates has capacitance of 9 pF. The separation between its plate is ‘d’. The space between the plates is now filled with two dielectrics. One of the dielectrics has dielectric constant k_{1}=3 and thickness 'd/3', while the other one has dielectric constant k_{2}=6 and thickness '2d/3'. Capacitance of the capacitor is now

(a) 1.8 pF b) 45 pF

c) 40.5 pF d) 20.25 pF

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