Exercise 1 1. They often make sandwiches for lunch. 2. I am not study at the moment. 3. I never study at night. 4. She talks to her friends every day. 5. She is not talking to her friends at the moment. 6. We have lessons every day. 7. We are not having an English lesson now. 8. He usually plays with Jim or Henry. Exercise 2 1. The telephone rang while I was having a hot shower. 2. When you phoned last night, I was reading a fantastic book. 3. Mary and I saw Henry while we were waiting for the bus this morning. 4. Last night we were having dinner with friends when Helen arrived. 5. While the teacher explained the problem, Lisa was dropping her books.
При последовательном соединении резисторов общим в цепи является ток, а напряжения на резисторах определяются из закона Ома для участка цепи. I = U/R ⇒ U = I×R. (1) Из формулы следует, что напряжения на резисторах прямо пропорциональны их сопротивлениям. Сопротивление второго резистора вдвое меньше (100/50=2), чем первого, поэтому и напряжение на нем будет вдвое меньше, чем на первом, т.е. U₂ = U₁/2 = 60 В. Напряжение на всем участке U = U₁+U₂ = 120+60 = 180 (B) Ток в цепи найдем из (1): I= 120/100 = 1.2 (A)
