问题 多选题

某电场中的一条电场线为直线,a、b为这条直线上的两点,如图所示 (  )

A.a点的场强一定大于b的场强

B.a点的电势一定高于b点的电势

C.把一负点电荷由b点从静止释放,在不计重力的情况下,一定向a点做匀加速直线运动

D.一负点电荷从a点向b点运动过程中,它的电势能一定增加

答案

A:由于a、b两点所在的电场线是直线,电场线的大小由电场线的疏密表示,一条电场线无法判断疏密,就无法确定a、b两处场强的大小.故A错误;

B:沿电场线的方向,是电势降落最快的方向,故B正确;

C:从b点由静止释放的负电荷,电荷能否做匀加速:只有在匀强电场中,才做匀加速运动.故C错误;

D:负电荷从a点移到b点,电场力做负功,电荷的电势能一定增大,故D正确.

故选:BD

单项选择题 B型题
单项选择题

For more than a decade, the prevailing view of innovation has been that little guys had the edge. Innovation bubbled up from the bottom, from upstarts and insurgents. Big companies didn’t innovate, and government got in the way. In the dominant innovation narrative, venture-backed start-up companies were cast as the nimble winners and large corporations as the sluggish losers.

There was a rich vein of business-school research supporting the notion that innovation comes most naturally from small-scale outsiders. That was the headline point that a generation of business people, venture investors and policy makers took away from Clayton M. Christensen’s 1997 classic, The Innovator’s Dilemma, which examined the process of disruptive change.

But a shift in thinking is under way, driven by altered circumstances. In the United States and abroad, the biggest economic and social challenges—and potential business opportunities—are problems in multifaceted fields like the environment, energy and health care that rely on complex systems.

Solutions won’t come from the next new gadget or clever software, though such innovations will help. Instead, they must plug into a larger network of change shaped by economics, regulation and policy. Progress, experts say, will depend on people in a wide range of disciplines, and collaboration across the public and private sectors.

"These days, more than ever, size matters in the innovation game," said John Kao, a former professor at the Harvard business school and an innovation consultant to governments and corporations. In its economic recovery package, the Obama administration is financing programs to generate innovation with technology in health care and energy. The government will spend billions to accelerate the adoption of electronic patient records to help improve care and curb costs, and billions more to spur the installation of so-called smart grids that use sensors and computerized meters to reduce electricity consumption.

In other developed nations, where energy costs are higher than in the United States, government and corporate projects to cut fuel use and reduce carbon emissions are further along. But the Obama administration is pushing environmental and energy conservation policy more in the direction of Europe and Japan. The change will bolster demand for more efficient and more environmentally friendly systems for managing commuter traffic, food distribution, electric grids and waterways.

These systems are animated by inexpensive sensors and ever-increasing computing power but also require the skills to analyze, model and optimize complex networks, factoring in things as diverse as weather patterns and human behavior. Big companies like General Electric and IBM that employ scientists in many disciplines typically have the skills and scale to tackle such projects.

In the author’s opinion, Obama’s approach to the health and energy problem()

A. is a doomed endeavor at its very beginning

B. typically illustrates the complexity of the situation

C. lacks a proper vision though effective in a short term

D. shows why large organizations are less innovative