Polarisation in a simple cell

Polarisation in a simple cell

ZIMSEC O Level Combined Science Notes: Perfecting the electric cell

Voltage/Potential difference

  • The voltage between the two electrodes is dependent on the type of electrode used
  • When magnesium and copper are used the potential difference between the two electrodes is fairly high
  • Enough current flows to even light a bulb
  • If copper and zinc are used the voltage is insufficient to light the lamp
  • The current can however be read on an ammeter
  • A voltmeter can also be used to measure the voltage of the cell
  • It will show that the magnesium-zinc battery produces a higher voltage and more current than a copper-zinc cell
Negative TerminalPositive Terminal
  • The table above shows the metals which could be used to make an electric cell
  • The least reactive metal can be used to make the positive terminal
  • The most reactive metal will be used to make the negative terminal
  • The further apart the minerals in the series the greater the potential difference (voltage)
  • For example the Magnesium-Copper cell gives the most potential difference
  • The Lead copper cell would give the least potential difference
  • A simple with a zinc plate for an electrode and
  • A copper plate for an electrode
  • and dilute sulphuric acid as an electrolyte
  • produces about 1 volt


  • After only a short time the cell stops working due to polarisation
  • Polarisation-this is when hydrogen bubbles collect on the copper plate of a simple electric cell and act as an insulator
  • Polarisation can be overcome by wiping the bubble off the plate at intervals
  • It can also be solved by adding a depolirising agent
  • A little potassium manganate (VII) to oxidise the hydrogen as soon as it forms

To access more topics go to the Combined Science Notes page.

Quick NetOne, Telecel, Africom, And Econet Airtime Recharge

If anything goes wrong, chat with us using the chat feature at the bottom right of this screen