Notes

• Electric field strength: It is the electric force experienced per unit +ve charge in the field
-> The direction of the force is determined by the charge:
1. If the charge is positive (+) the force is in the "same" direction as the E field (accelerate)
2. If the charge is negative (-) the force is in the "opposite" direction to the E field (decelerate)
• Note: the force will always be parallel to the electric field lines
-> If conductor is positively (+) charged, the field lines are directed "away" from the centre of the sphere
-> If conductor is negatively (-) charged, the field lines are directed "towards" the centre of the sphere
• This equation (E = ΔV/Δd) cannot be used to find the electric field strength around a point charge (since this would be a radial field)
• v^2 (speed) is directly proportional to V (voltage), even if we have parallel/non parallel charged plates
-> The amount of deflection depends on the following properties of the particles:
1. Mass – the greater the mass, the smaller the deflection and vice versa
2. Charge – the greater the magnitude of the charge of the particle, the greater the deflection and vice versa
3. Speed – the greater the speed of the particle, the smaller the deflection and vice versa
-> If there is a +ve and -ve charge, then the electrostatic force is -ve, this can be interpreted as an "attractive force"
-> If the charges are the same, the electrostatic force is +ve, this can be interpreted as a "repulsive force"
• Electric Potential: Work done per unit +ve charge to bring a +ve test charge from infinity to a point
-> When a test charge moves closer to a -ve charge, its electric potential "decreases"
-> When a test charge moves closer to a +ve charge, its electric potential "increases"
• Potential gradient: The rate of change of electric potential with respect to displacement
• Magnitude of electruc field strength = potential gradient
-> The electric potential changes according to the charge creating the potential as the distance r increases from the centre:
1. If the charge is positive, the potential decreases with distance
2. If the charge is negative, the potential increases with distance
• Electric potential energy: The work done in bringing a charge from infinity to that point
• Charge is lost by: Air is humid, Sphere is not smooth, Heat
• Spheres are of metal and thus charges can flow within them, therefore the charges align themselves in such a way that the net force is zero which means no electric field (explaining why electric field strength is zero)
• In E vs r/ V vs r graph the charge from which the null point is further away is the greater charge
• If the charges have equal radii then look at initial value of E or V
-> Like charges will have null point (E = 0)
-> Unlike charges won't have null point

ET PHYSICS
• Potential energy: The ability to do work as a result of the position of the object