31.Three timer.Consider three vacuum-filled parallel-plate capacitors, each with chargeQ,whose properties are listed in the table shown. Which of the following is the correct rela-tionship among the energies stored in each capacitor?CapacitorAreaSeparation DistanceX2A3dY4Ad/5ZA/52d A.UX< UY< UZB.UZ< UY< UXC.UZ< UX< UYD.UY< UX< UZSolution:The capacitance of the parallel-plate capacitor isC=ε0Adand the energy stored in the capacitor isU=12Q2C=dQ22ε0ATherefore, the energy stored in each capacitor isUCapacitor X32dQ22ε0ACapacitor Y120dQ22ε0ACapacitor Z10dQ22ε0AA – 17
Sample Exam Second Semester, AY 2016–2017 Physics 72 32.Kwatro Kantos.What happens to the energy density inside a vacuum-filled parallel-platecapacitor if the electric field magnitude between the plates is increased by a factor of4? 33.Capacitance.A spherical vacuum-filled capacitor with inner and outer radii ofRand2R,respectively, has a capacitance ofC. If the outer radius is increased to3R, what will be thenew capacitance?
Sample Exam Second Semester, AY 2016–2017 Physics 72 35.Can you handle my drift?A current is travelling along a wire.The cross-sectionalarea of the wire suddenly increases by15%. If the current and the free-electron densityare maintained, what is the new drift velocity of the electrons in terms of the initial driftvelocity~vd?
You've reached the end of your free preview.
Want to read all 24 pages?
- Spring '11