Energy Stored by a Capacitor

• What does a power supply do when charging a capacitor?

  Pushes electrons from positive to negative plate

  
• What happens to electrical energy when a capacitor is charged?

  It becomes stored on the plates
• How does charge build up on a capacitor?

  Initially small, then gradually increases
• Why is it easier to add electrons to the negative plate initially?

  There is little repulsion at first
• What happens as the negative plate becomes more negatively charged?

  Repulsion force between electrons increases

  
• What occurs to the potential difference as charge increases?

  It increases as charge increases
• How is charge Q related to potential difference V in a capacitor?

  Q is directly proportional to V

  
• What does the graph of charge against potential difference look like?

  A straight line graph through the origin

  
• How can electrical energy stored in a capacitor be determined?

  From the area under the potential-charge graph

  
• What is the formula for the area of a right-angled triangle?

  Area = 0.5 × base × height
• What does E represent in the energy stored equation?

  Work done or energy stored (J)
• What is the relationship between charge Q and capacitance C?

  Q = CV

  
• How can energy stored be defined in terms of charge Q and capacitance C?

  Using the equation E = 0.5 × Q × V

  
• What is the electric potential energy stored on a sphere charged to 100 kV with charge 1.8 μC?

  0.09 J
• How is the energy stored calculated from the area under the graph?

  It equals the area of a right-angled triangle
• What is the equation for energy stored in terms of capacitance C and potential difference V?

  W = 0.5 × CV²

  
• How is the change in energy stored related to the change in potential difference?

  It is proportional to the change in p.d.

  
• What is the change in energy stored when capacitance is 1500 μF and potential difference changes from 10 V to 30 V?

  0.6 J
• What are the three equations for energy stored in a capacitor?

  1. E = 0.5 × Q × V
  2. E = 0.5 × C × V²
  3. E = Q² / (2C)
• What steps should be taken to determine the energy stored in a capacitor?

  1. Identify given variables (C, Q, V)
  2. Choose the appropriate energy equation
  3. Substitute values into the equation
  4. Calculate the energy stored