问题 问答题

探究“电流跟电压、电阻关系”的过程中,某同学按如图1所示的电路图连接实物,请你用笔画线代替导线帮他将图2实物电路连接好.要求滑片在右端时滑动变阻器连入电路的阻值最大.

步骤1:保持定值电阻R的阻值不变,闭合开关S后,使R两端的电压成整数倍变化,如2V、4V、6V,分别读出并记录对应于不同电压下的电流表示数,比较每次电流表的示数是否成整数倍变化.

步骤2:保持每次定值电阻两端电压不变,换用不同的定值电阻,使电阻成整数倍变化,如5Ω、10Ω、15Ω,分别读出并记录对应于不同阻值的电流表的示数,比较每次的电阻值与电流值的乘积是否相等.

(1)“步骤1”的设计目的是为了探究______.

(2)当某同学在按“步骤2”做时,选一个“5Ω”的电阻,测得电流表示数为0.2A,当换“10Ω”来做时,发现电流表的示数不是0.1A(不考虑温度对电阻的影响),你认为电流表的度数将会______(填“大于”或“小于”)0.1A,滑片应该向______(填“左”或“右”)移动.

答案

由电路图可知,电源、开关、滑动变阻器、定值电阻、电流表组成串联电路,电压表与定值电阻并联,滑片在右端时滑动变阻器连入电路的阻值最大.则将滑动变阻器滑片左边的电阻连入电路,即将接线柱接在左下边的接线柱,实物电路图如图所示.

(1)由实验步骤1可知,实验时控制电阻两端电压不变而改变电阻阻值,测出通过电阻的电流,实验是为了探究电流与电阻的关系.

(2)步骤2中,定值电阻由“5Ω”换为“10Ω”,根据串联分压,其两端电压也会相应增大,因此,电流不会从O.2A变小到0.1A,而是大于这一数值;

要想使电流减小一倍,应调节滑动变阻器的滑片向右移动,使定值电阻两端的电压保持与第一次相同才行.

故答案为:如上图;

(1)电流与电压的关系;(2)大于;右.

阅读理解

Beaches Cross-Training Club

Halloween Fun Run

Start date: Sept. 9---Oct. 28

Rate: $80 / $10 per class

Time: 4:15---5:15

Dress according to weather. Please note that your child does not need to run races in order to participate in this run training. Focus is on fun and participation. No run experience needed. All ages of kids are welcome.

Class format: 40 minutes of running and running games.

Saturday Indoor Long Rides 2---5 pm

Start date: Sat. Oct.17---Dec.19

Pre-registered rate: $200 / $ 20 per ride

Drop-in rate: $22

This class is designed for road riders, Ride to Conquer Cancer participants, athletic cross-training, and people wanting a great weekly challenge. Participants are encouraged to work within their own level of comfort. No previous riding experience needed; all are welcome. We will begin long rides at 2 hours, and after a few weeks add 15 minutes until we reach 3 hours. At that point, rides will remain 3 hours in length until the outdoor season begins.

Please bring liquid that you drink, nutrition and a towel. Room accommodates 18 spin bikes(健身车).

Family Fun Fit Private Coaching

Learn with Christina Kaufmann. Family Fun Fit’s Private Coaching Service begins with a one-hour face-to-face meeting where we map out where you are and where you wish to be. Next, Christina creates a personalized training program and schedule that will systematically train you and encourage you to achieve your desired goal.

Clients(顾客) have the access to the coach via email or phone. Christina’s past clients have successfully achieved their goals.

This service is ongoing(进行中). Cost is $150 per month.

小题1:Halloween Fun Run is held to make kids ______.

A.learn how to compete

B.become professional runners

C.have a good time

D.build self-confidence小题2:When you attend Saturday Indoor Long Rides, you’re required to _____.

A.begin long rides at three hours

B.have precious riding experience

C.prepare some drinks

D.be a road rider小题3:What do we know about Christina Kaufmann ?

A.Her class is very lively and interesting.

B.She gives her instructions on the phone in most cases.

C.She offers service for free.

D.She helps make training plans.小题4:What’s the purpose of the text ?

A.To introduce Christina Kaufmann.

B.To help people form good habits.

C.To try to teach people how to keep fit.

D.To encourage people to join the club.

单项选择题