题干

为探究“影响电磁铁磁性强弱的因素”,刘洋用电池(电压一定)、滑动变阻器、数量较多的大头针、铁钉以及较长导线为主要器材,进行如图所示的简易实验.

(1)他将导线绕在铁钉上制成简易电磁铁,并巧妙地通过____ 来显示电磁铁磁性的强弱,下面的实验也用这种方法的是____ 

A.认识电压时,我们可以用水压来类比

B.用磁感线来描述看不见的磁场

C.用煤油温度升高的多少来显示电流通过导体产生的热量多少

D.探究导体电阻大小与哪些因素有关时,各个因素分别研究

(2)连接好电路,使变阻器连入电路的阻值较大,闭合开关,观察到如图甲所示的情景.接着,移动变阻器滑片,使其连入电路的阻值变小,观察到图乙所示的情景,比较图甲和乙,可知____ 图中的电流较小,从而发现,通过电磁铁的电流越____ (选填“大”或“小”)磁性越强.本实验中还可以改变____ 来改变电磁铁的磁性强弱.

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答案(点此获取答案解析)

吸引大头针的多少,C,甲,大,螺线管的匝数

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    To meet the global climate crisis that is approaching, big lifestyle changes are required of those of us. The good news is that our way of life can remain meaningful and worthy as our consumption becomes sustainable(可持续发展的).

    ____ Eat less meat and move toward a plant-based diet. This is one of the most effective things we can do because the food we now produce and consume is destroying the very ecosystems that we depend upon for survival. Here are some of the grim facts.

    The U. S. uses about one-half of its land for agriculture.____For example, the U. S. uses over 90 million acres of good agricultural land to produce corn, which is mostly fed to livestock(家畜).

    With 7.6 billion people on earth, the demand for food is enormous and constantly on the rise. It's easy to feel we can't make a difference____We should not ignore the power of the choices we make.

    Even one person can make a big difference by eating less meat and moving toward a plant-based diet and make contributions to the health of the planet as well as your own. Recognize how the food we eat is connected to other living beings. It often helps us make much wiser buying choices.____This way, we will help people around the world enjoy more eco-friendly and nutritious foods.

    ____When you change your diet to be more sustainable, you become visible proof that changing our food habits is doable, healthy, and enjoyable.

A. Little things matter in your relationship with the earth.

B. By buying mindfully, we support local, affordable agriculture.

C. But we can change our diet to heal the earth as we heal ourselves.

D. Unfortunately, the majority is used to raise livestock or for crops consumed by them.

E. Your choices create positive impacts on the food system and inspire the people around you.

F. There's one step you can take right away to reduce harm to Mother Earth.

G. We can try to reduce waste by using leftovers and eating the fresh produce we buy.