Electric Fields — MS 模式

定义题模式

术语	分值	标准答案
electric field	B1	force per unit positive charge
electric field strength	B1+B1	force per unit charge + exerted on a positive charge / placed at a point
electric potential	M1+A1	work done per unit charge + moving a positive charge from infinity
capacitance	M1+A1	charge per unit potential difference + charge on one plate / p.d. across plates

计算题模式

公式	标记	典型代入
$E = Q / (4\pi \epsilon_0 r^2)$	C1+A1	注意 $r$ 从中心算起
$V = Q / (4\pi \epsilon_0 r)$	C1+A1	代数叠加
$F = Q_1 Q_2 / (4\pi \epsilon_0 r^2)$	C1+C1+A1	代入数值 + 8.99 × 10$^9$
$E = V/d$	C1+A1	单位转换
$\frac{1}{2} mv^2 = qV$	C1+C1+A1	能量守恒求速度

对比题模式

对比	标记	要点
similar	B1	both inverse square law / both radial / both $1/r^2$
different	B1	electric can be attractive or repulsive / gravitational only attractive
compare potentials	B1	both $\propto 1/r$ / same sign or opposite sign

作图题模式

图形	标记	要点
field lines between plates	B1+B1+B1	parallel + equally spaced + arrows + straight
$E$-$r$ for sphere	B1+B1+B1	$E = 0$ inside + $E \propto 1/r^2$ outside + starts at $E_0$
path of particle	B1+B1	curved (parabolic) + straight after field
$V$-$r$ for sphere	B1+B1+B1	constant inside + $V \propto 1/r$ outside

关键词速查

关键词	含义
force per unit positive charge	电场强度定义
work done per unit charge	电势定义
from infinity	电势参考点
inverse square law	反平方定律
radial field	径向场
uniform field	匀强场
potential gradient	电势梯度
$E = -dV/dr$	场强与电势关系