Active-Passive Voice - Food for Thought

Sometimes it is not necessary to mention the agent in the Passive Voice, and it makes good English. Look at some examples, and discuss them with your teacher :

Active : People voted the leader to power.

Passive : The leader was voted to power. (Think : Is 'by people' needed here?)

Active : You should cross the road carefully.

Passive : The road should be crossed carefully. (Think : Is 'by you' really needed here?)

Active : The enemy killed the soldier in a battle.

Passive : The soldier was killed in a battle. (Think : Is 'by the enemy' needed here?)

Active : A pickpocket picked my pocket.

Passive : My pocket was picked. (Think : Is 'by a pickpocket' needed here?)

Active : The judge disqualified Lalu from his membership.

      Passive : Lalu was disqualified from his membership. (Think : Is 'by the judge' needed here?)