现将一螺线管的线圈重绕，半径为原来的一半，保证导线长度不变，单位长度上的匝数不变，重绕后，螺线管的自感与原来相比将变（)
A. 原来的2倍
B. 原来的1/2倍
C. 原来的4倍
D. 原来的1/4倍
查看答案
当线圈通有稳恒电流时，线圈中产生自感电动势。
A. 对
B. 错
当回路中电流发生变化时，回路中产生自感电动势。
A. 对
B. 错
[音频]【单选题】 Questions 5 to 7 are based on the news report you have just heard.Question 5: What did drivers on the motorway to Warsaw find?
A. The road was flooded.
B. The road was blocked.
C. The road was frozen with snow.
D. The road was covered with spilled gas.
微信支付 
支付宝支付