如图，一理想变压器原线圈接稳压交变电源，副线圈接电阻R₀和滑动变阻器R，原、副线圈电路中分别接有理想电流表和理想电压表。现闭合开关，滑动头P从a端向b端移动，则（  ）

A mgsinθ B ftmgcosθ C mg(sinθ-μcosθ) D mg(sinθ+μcosθ)

A 内能增加，压强增大 B 内能增加，压强减小 C 内能减少，压强增大 D 内能减少，压强减小

A 频率变小，波长变长 B 频率不变，波长变长 C 频率不变，波长变短 D 频率变小，波长变短

A <img width="24" height="33" src="https://www.beizhujiaoyu.com/uploads/202208/20210727163353_2746.jpg" /> B <img width="24" height="32" src="https://www.beizhujiaoyu.com/uploads/202208/20210727163354_4309.jpg" /> C <img width="18" height="33" src="https://www.beizhujiaoyu.com/uploads/202208/20210727163355_3684.jpg" /> D <img width="26" height="33" src="https://www.beizhujiaoyu.com/uploads/202208/20210727163356_4933.jpg" />

A <img width="51" height="32" src="https://www.beizhujiaoyu.com/uploads/202208/20210727163402_7902.jpg" /> B <img width="118" height="31" src="https://www.beizhujiaoyu.com/uploads/202208/20210727163403_7122.jpg" /> C <img width="80" height="31" src="https://www.beizhujiaoyu.com/uploads/202208/20210727163404_8683.jpg" /> D W_f=Fs

A E_O>E_P，U_O>U_P B E_O<E_P，U_O>U_P C E_O>E_P，U_O<U_P D E_O<E_P，U_O<U_P

A H₂ B SiO₂ C MgSO₄ D MgO

A SO₂ B He C NH₃ D HCl

A Cu B Zn(OH)₂ C Cu²⁺ D Zn

A 1．2mol／(L·min) B 6．0mol／(L·min) C 0．6mol／(L·min) D 0．4mol／(L·min)