题干

两只相同的电阻,分别通以正弦波形的交流电和方波形的交流电,两种交流电的最大值相等,且周期相等.在正弦波形交流电的一个周期内,正弦波形的交流电在电阻上产生的焦耳热为Q1,方波形的交流电在电阻上产生的焦耳热Q2 .则Q1∶Q2之比等于( )

  

A:1∶1 

B:2∶1 

C:1∶2 

D:4∶3

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答案(点此获取答案解析)

C

同类题1

阅读下面短文,从每题所给的A、B、C和D四个选项中,选出最佳选项。

A

Safety and Security Procedures

   Your safety and the security of your personal property(财产) are of the primary concern to those of us who welcome you as our guest. We urge you to take advantage of the following suggestions.

 YOUR VEHICLE

   Lock your vehicle and do not leave money or valuable items inside. We are not responsible for their loss.

TRAVELING

   Be good at noticing things around you when sightseeing or traveling. Stay in heavily traveled areas. Don't display large amounts of cash.

GUEST ROOM SECURITY

   For additional security, use the deadbolt (插锁) provided on your door and make sure the windows are locked. As an additional precautious measure, please secure the secondary locks provided. Do not admit anyone to your room without first making identification. A one-way viewer is provided in your door to assist with identification. If there is any doubt about the person's identity, please contact the Front Desk.

SAFETY BOXES

   Do not leave money or valuables in your room or vehicle. We provide free safety boxes for you. We are not responsible for items left in room valued over $200.

KEYS

   Safeguard your key. Please do not leave it in the door. Do not give your key to others or leave it unattended. Please leave your key at the Front Desk when you check out.

FIRE

   Please familiarize yourself with the nearest fire exits. Report fire or smoke to the hotel operator. In the unlikely event of a fire, please move quickly and calmly to the nearest safe exit and leave the building. Avoid the use of the elevator.

REPORTING

   Please report any suspicious activity, or safety concerns to management.