Usually, in a passive clause we use "by" to introduce the "agent"--its the person or thing that does the action or that causes what happens.(But remember that agents are mentioned in only about 20 percent of the passive clauses.) Here are some examples: 1. These robots are made by the children in Japan. 2. The problem in the company was made by the new secretary who forgot about the meeting with Mr. Lim. 3. The success of the project was caused by everyone's cooperation and dedication at work. 4. These coin purse are made by children in the orphanage. 5. The trouble was caused by the reckless driver! |
Also, note that some participles can be more like adjectives than verbs. For example shocked, worried or frightened. After these,we often use prepositions instead of by. Here are some examples: 1. The family was worried about/by her loss. 2. Her dad was shocked at/by her attitude in the reunion. 3. Are you frightened of snakes and other insects? 4. I am worried about/by the weather forecast. 5. Lea was shocked at/by the current news about her best friend and schoolmate. |
Note also that "with" is used to talk about an instrument which is used by an agent to do an action. Here are some examples: 1. The robber was shot (by the policeman) with his gun. 2. He paid his bill (by phone) through online banking. 3. The 10 year old boy was hit (by his dad) with his belt because he was very hard headed. |