题干

图示是霍尔元件的工作原理示意图,磁感应强度为B的匀强磁场垂直于霍尔元件的三作面向下,通入图示方向的电流I,C、D两侧面会形成电势差UCD,下列说法正确的是(该元件正常工作时,磁场必须垂直工作面)(   )

A:电势差UCD仅与材料有关

B:若霍尔霉件的自由电荷是自由电子,则c侧的电势低于D侧的电势

C:其他条件不变,仅增大匀强磁场的磁感应强度时,电势差UCD变大

D:在测定地球赤道上方的地磁场强弱时,元件的工作面应保持水平

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答案(点此获取答案解析)

B,C

同类题3

根据短文内容, 从短文后的选项中选出能填入空白处的最佳选项。选项中有两项为多余选项。

    ____

    Self-worth is very important in your life. We may love others, but we need to learn to love ourselves. We have to believe in what we do, and feel better about ourselves. If you do not have self-worth, you may begin to get discouraged.

    Avoid negative people in your life. ____If these people put you down, do not believe in you, or treat you badly, why are you still around them? It took me years to realize this for myself, and it is true. Negative people hurt your self-worth, and bring you down emotionally. Get closer to people that believe in you. If you do not have these positive people in your life, find a support group that can help you. ____Your self-worth can be increased greatly with positive guide.

    Find employment or volunteer somewhere you feel valued, or can make a difference. Giving to others builds you up personally. You do not have to do this all the time, but once you see how good it feels you will want to continue.

    ____Think about what you can do to change your future. Make a list of steps you can take to improve your life. Stall setting goals in your life. Goals give us something to focus on, and we push to achieve them. These can be whatever goals you would like to finish, be sure they are achievable Goals. ____

    Doing the above steps can greatly increase your self-worth, and remember you are worth it.

A. Stop thinking about the past as you can't change it.

B. Keep the saying of "No pain, no gain" in mind.

C. Increase Your Self -Worth and Feel Better about Yourself.

D. Believe You can Be the King of the World Even When You Fail.

E. Once you set your goals, you will start pushing for more.

F. These people are likely to believe in us even when we do not have confidence.

G. This could be your husband, boyfriend, other family members, or even friends.