Any of three conditions may warrant using a passive sentence rather than an active sentence:
1. Use a passive sentence when the receiver of the action is more important to the reader than the actor.
Since the strongest part of a sentence is the opening, the element appearing first will gain the greater attention. If the receiver of the action is the important element, its location at the beginning of the sentence will give it more emphasis.
Note the shift in emphasis when the passive sentence structure is used:
ACTIVE
Our chemists have developed a chip-resistant coating
using isothermal curing.
PASSIVE
A chip-resistant coating using isothermal curing has been
developed by our chemists.
ACTIVE
We employed numerous cross-checking mechanisms
during the last experimental exercise which were
extremely valuable in validating the data received.
PASSIVE
Numerous cross-checking mechanisms were employed
during the last experimental exercise which were
extremely valuable in validating the data received.
2. Use a passive sentence when the actor is unknown or is best left unidentified.
To be grammatically correct, active sentences must include an actor, either real or understood. If the actor is unknown, a passive sentence may communicate the real intent of the message less awkwardly.
ACTIVE
Someone misfiled the audit report on last year's activities.
PASSIVE
The audit report on last year's activities was misfiled.
Similarly, tact may dictate moving the focus away from the actor without changing the basic message content.
ACTIVE
Unfortunately, you failed to send us your order on time.PASSIVE
Unfortunately, your order was not received in time.
3. Use a passive sentence to make a smooth transition between sentences.
For ease of understanding, key words in sentences must be near enough to each other to suggest a sentence connection. A passive sentence often helps to accomplish that transition.
ACTIVE/ACTIVE
Assignment to teams will occur following interviews.
Work-team leaders will conduct all interviews.ACTIVE/PASSIVE
Assignment to teams will occur following interviews.
All interviews will be conducted by work-team leaders.