Electric field, potential and energy Topic 9.3 (AHL)

Remember? Define potential difference (voltage).Define potential difference (voltage).

Remember? Amount of electrical energy converted to heat when a charge flows through a resistor.Amount of electrical energy converted to heat when a charge flows through a resistor.

EPE Draw the electric field lines.Draw the electric field lines.

EPE If a positive charge was placed in the plate. Which direction will it move?If a positive charge was placed in the plate. Which direction will it move?

EPE Which direction will require you to do some work?Which direction will require you to do some work? When you do this work will it increase its KE or PE?When you do this work will it increase its KE or PE?

EPE What’s the direction of the electric force on positive charge? State equationWhat’s the direction of the electric force on positive charge? State equation

EPE F= Eq, then to move the positive charge from negative to positive plate, we need to apply equal and opposite force.F= Eq, then to move the positive charge from negative to positive plate, we need to apply equal and opposite force.

EPE Therefore the work done = Fd = Eqd = EqhTherefore the work done = Fd = Eqd = Eqh We increased the electrical PE (EPE)We increased the electrical PE (EPE)

Electric potential Where will you have the greatest electrical potential energy?Where will you have the greatest electrical potential energy? Can you define electric potential at a point? (remember gravitational potential and change the terms)Can you define electric potential at a point? (remember gravitational potential and change the terms)

Electric potential Where will you have the greatest electrical potential energy?Where will you have the greatest electrical potential energy? Can you define electric potential at a point? Work done per unit charge taking a small positive test charge from infinity to a point.Can you define electric potential at a point? Work done per unit charge taking a small positive test charge from infinity to a point. Unit?Unit?

Electric potential Where will you have the greatest electrical potential energy?Where will you have the greatest electrical potential energy? Can you define electric potential at a point? Work done per unit charge taking a small positive test charge from infinity to a point.Can you define electric potential at a point? Work done per unit charge taking a small positive test charge from infinity to a point. Unit? JC -1 or VoltsUnit? JC -1 or Volts Potential is a scalar quantityPotential is a scalar quantity Reminder : at infinity you have zero potential (like gravitational) Reminder : at infinity you have zero potential (like gravitational)

Electric potential Where will you have zero potential?Where will you have zero potential? Greatest potential?Greatest potential? Equal potential (equipotential)Equal potential (equipotential)

Electric potential Where will you have zero potential? bottomWhere will you have zero potential? bottom Greatest potential? TopGreatest potential? Top Equal potential (equipotential)Equal potential (equipotential)

Electric potential Equation for change in potential?Equation for change in potential?

Electric potential Equation for change in potential?Equation for change in potential?

Electric potential Draw field lines and equipotential lines for the a positive test charge.Draw field lines and equipotential lines for the a positive test charge.

Electric potential Draw field lines and equipotential lines for the a positive test charge.(red: equipotential line, black: field lines)Draw field lines and equipotential lines for the a positive test charge.(red: equipotential line, black: field lines)

Electric potential Draw field lines and equipotential lines when two positive charges are brought close to each other.Draw field lines and equipotential lines when two positive charges are brought close to each other.

Electric potential Draw field lines and equipotential lines when two positive charges are brought close to each other.Draw field lines and equipotential lines when two positive charges are brought close to each other. Try other patterns on simulation.Try other patterns on simulation.

Force VS distance graph Force more or less if two positive charges get closer to each other? Predict shape of graphForce more or less if two positive charges get closer to each other? Predict shape of graph

Force VS distance graph Force more or less if two positive charges get closer to each other? Predict shape of graphForce more or less if two positive charges get closer to each other? Predict shape of graph gravitational electrical

Force VS distance graph What will the area represent? EquationWhat will the area represent? Equation electrical

Force VS distance graph What will the area represent? EquationWhat will the area represent? Equation electrical

Potential vs distance How will the graph look like for a positive charge?How will the graph look like for a positive charge?

Potential vs distance Potential inside positive sphere is constantPotential inside positive sphere is constant What will the tangent represent?What will the tangent represent?

Potential vs distance What will the tangent represent?What will the tangent represent? -E (since E will be positive)-E (since E will be positive) x

E and V graphs

Wells and hills In gravitational we saw the wellsIn gravitational we saw the wells

Wells and hills In electrical it can be both wells and hills.In electrical it can be both wells and hills. Well is potential is decreasing as you approach ? chargeWell is potential is decreasing as you approach ? charge Hill if potential increasing as you approach ? chargeHill if potential increasing as you approach ? charge

Wells and hills In electrical it can be both wells and hills.In electrical it can be both wells and hills. Well is potential is decreasing as you approach negative chargeWell is potential is decreasing as you approach negative charge Hill if potential increasing as you approach positive chargeHill if potential increasing as you approach positive charge A combination of positive and negative charge is called a dipole

Addition of potential Potential is scalar therefore add without considering directionPotential is scalar therefore add without considering direction +– P

Questions 30,31 P.203 Which charge is positive which is negative and explainWhich charge is positive which is negative and explain If a positive charge is placed at A, would it move? In which direction if yesIf a positive charge is placed at A, would it move? In which direction if yes In which point is the field strength greatest?In which point is the field strength greatest?

Questions 30,31 P.203

comparison