• The magnitude of the electric field strength in a?uniform?field between two charged parallel plates is defined as:

• Where:
  • E?=?electric field strength?(V m-1)
  • V?= potential difference between the plates (V)
  • d?= separation between the plates (m)

   

• The electric field strength is now defined by the units?V m–1
  • Therefore, the units V m–1?are equivalent to the units?N C–1
• The equation shows:
  • The greater the?voltage?(potential difference) between the plates, the?stronger?the field
  • The greater the?separation?between the plates, the?weaker?the field

   

• Remember this equation?cannot?be used to find the electric field strength around a?point charge?(since this would be a radial field)
• The direction of the electric field is from the plate connected to the?positive?terminal of the cell to the plate connected to the?negative?terminal

The E field strength between two charged parallel plates is the ratio of the potential difference and separation of the plates

• Note:?if one of the parallel plates is?earthed, it has a voltage of 0 V

Step 1: Write down the known values

• • Potential difference,?V?= 7.9 kV = 7.9 × 103?V
  • Distance between plates,?d?= 3.5 cm = 3.5 × 10-2?m
  • Charge,?Q?= 2.6 × 10-15?C

   

Step 2:?Calculate the electric field strength between the parallel plates

Step 3:?Write out the equation for electric force on a charged particle

F?=?QE

Step 4: Substitute electric field strength and charge into electric force equation

F?=?QE?= (2.6 × 10-15) × (2.257 × 105) = 5.87 × 10-10?N = 5.9 × 10-10?N (2 s.f.)