kitkat794
- 1
- 0
Homework Statement
i've been trying to do these but i keep getting different answers from back of book.
1)When there is a potential difference of 1.0 V between two points in an electrical ciruit, what is the mean amount of energy lost by an electron when moving between these two points? This amount of energy has a special name, the electronvolt, symbol eV.
2)When an electron is accelerated across a potential difference of about 15 V it has enough energy to ionise a nitrogen atom, that is, to remove an electron from the atom by collision with it. How many attojoule, aJ is this? 1.0aJ=1.0 x 10^-18 J.
3) The electrical circuit in a small torch consists of a battery of e.m.f 3.0 V and a bulb in series. The potential difference across the bulb is 2.7 V when the current in the bulb is 0.3 A.
a) Calcuate how much energy is converted in one minute:
i) from chemical form to electrica form in battery
ii) from electrical form to thermal energy and light in the bulb
Homework Equations
The Attempt at a Solution
1) ?
2) 1 volt= 1 joule per couloumb second so 15V = 15 joules percoloumb second. then i did 15 divided by 1x10^-18 and i got 1.5 x10^19 aJ which is wrong (should be 2.4aJ)
3)a) i know i meant to use the formula for electromotive force but i don't know how to work out the charge to put it in this (answer should be 54J)
ii) use formua for potential difference which again needs charge and i don't know how to work it out (answer should be 48.6 J)