2-potential.pdf - electric potential and capacitance physics 111N electric potential energy consider a uniform electric field(e.g from parallel plates

# 2-potential.pdf - electric potential and capacitance...

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physics 111N electric potential and capacitance
physics 111N 2 electric potential energy ! consider a uniform electric field (e.g. from parallel plates) ! note the analogy to gravitational force near the surface of the Earth
physics 111N 3 potential between parallel plates + + + + + + + + + + ! ! ! ! ! ! ! ! ! ! define a quantity that depends only upon the field and not the value of the test charge the ‘potential’ measured in Volts, V = J/C potential energy actually only differences of potential are meaningful, we can add a constant to V if we like
physics 111N 4 potential between parallel plates + + + + + + + + + + ! ! ! ! ! ! ! ! ! ! 0 V 2.25 V 4.50 V 0 V 9 V 9.00 V 6.75 V equipotential lines lines of equal value of potential arbitrarily choose V =0 at the right-hand plate
physics 111N 5 a capacitor + + + + + + + + + + ! ! ! ! ! ! ! ! ! ! 0 V 2.25 V 4.50 V 9.00 V 6.75 V
physics 111N 6 conservation of energy using potential A 9 V battery is connected across two large parallel plates that are separated by 9.0 mm of air, creating a potential difference of 9.0 V. An electron is released from rest at the negative plate - how fast is it moving just before it hits the positive plate ? + + + + + + + + + + ! ! ! ! ! ! ! ! ! !
physics 111N 7 potential energy between point charges + Q + Q
physics 111N 8 potential from a point charge arbitrarily choose V =0 infinitely far from the charge depend only on distance from the charge Q
physics 111N 9 a set of point charges q 1 q 2 q 3 P at the point P there is an electric field E and an electric potential V
physics 111N 10 electric field from a set of point charges q 1 q 2 q 3
physics 111N 11 electric field from a set of point charges q 1 q 2 q 3
physics 111N 12 electric field from a set of point charges q 1 q 2 q 3 have to do vector addition - difficult !
physics 111N 13 electric potential from a set of point charges q 1 q 2 q 3 just scalar addition - easy !
physics 111N + + ! 14 for example 10.0 mm 4.00 mm 5.00 mm +10.0 pC +20.0 pC -8.0 pC find the electric potential what potential energy would a charge of 2.0 nC have at this position ?
physics 111N 19 equipotential diagrams equipotentials are defined as the surfaces on which the potential takes a constant value - hence different equipotentials never intersect usually draw them with equal potential separations
physics 111N 20 equipotentials for a point charge 30 V 50 V 70 V 90 V 110 V
physics 111N 21 equipotentials from a dipole + ! +20 V -20 V 0 V
physics 111N 22 equipotentials from a dipole +20 V -20 V notice that the field lines are always perpendicular to the equipotentials
physics 111N 23 equipotentials from two equal point charges notice that the field lines are always perpendicular to the equipotentials

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• Spring '20
• Energy, Electric charge, Electric potential energy

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