1. can someone please explain the idea of a dielectric to me (or at least give me a link that explains it in laymans terms) - all i understand is that its placed between two capacitors and it increases their capacitance (by the factor of K). what does it do to the voltage? and the charge? 2. a question states that a fully charged capacitor of capacitance 1.0 F is able to light a .50 watt bulb for 5.0 seconds before it quits - what was the terminal voltage of the battery that charged the capacitor? I first tried wolving for work (power = work/time) and I got W = 2.5 J but after that im stuck. i know that V = W/q but i dont know what q is. please help. 3. the last question says to store energy to trigger an electronic flash unit for photography, a capacitor is connected to a 400 V voltage source. the flash requires 20 J. the capacitor is initially airfilled and has a capacitance of 100 uF (microfarads). you then insert a dielectric material, leaving everything else the same. what must be the dielectric constant to store 20 J. my solution: I started by saying that U = 1/2 CV^2 (is that correct?) by solving for C required I got 2.5*10^-4 F however, it says my capacitance is only 100 uF = 1*10^-4 F therefore the dielectric constant needs to be (2.5*10^-4)/(1*10^-4) = 2.5 is that the right answer? did i do the work correctly? thanks for the help.