P2- current electricity

electrical charges

• two insulating material rubbed together= electrons rubbed off one and deposited on the other
• electrons have negative charge so material gaining the electrons becomes negatively charged, the object which has lost the electrons becomes positively charged
• on a polythene rod the electrons are gained so it becomes negative and the cloth becomes positive as it looses the electrons
• this process is called charging by fricition
• two objects with opposite charge= attract
• two objects with same charge= repel
• bigger distance between two objects= smaller force

electric circuit

• current= charge/ time
• 

resistance

• current(amps) through a circuit measured by an ammeter
• ammeters always placed in series component
• the potential difference(volts) of a component measured by a voltmeter
• voltmeter is always placed in parallel with component
• potential difference= work done/ charge (columbs)
• resistance is the opposition to current flow
• resistance(ohms)= pd/current
• ohms law= if a resistor is kept at constant temp the current potental difference graph shows a straight line passing through origin…