# Current of electricity – CIE AS Level Physics 9702

Contents:-

• Electric current
1. understand that electric current is a flow of charge carriers
2. understand that the charge on charge carriers is quantised
3. define the coulomb
4. recall and use $$Q = It$$
5. derive and use, for a current-carrying conductor, the expression I = Anvq, where n is the number density of charge carriers
• Potential difference and power
1. define potential difference and the volt
2. recall and use $$V = \frac{W}{Q}$$
3. recall and use $$P = VI$$ and $$P = I^2R$$
• Resistance and resistivity
1. define resistance and the ohm
2. recall and use $$V = IR$$
3. sketch and discuss the $$I-V$$ characteristics of a metallic conductor at constant temperature, a semiconductor diode and a filament lamp
4. state Ohm’s law
5. recall and use $$R = \frac{\rho L}{A}$$

Video (1:47:19 mins)