帶正電的金屬球接地，附近並沒有其他帶電物體。下列哪些敘述必定是正確的？

（1）正電荷從金屬球轉移到地球。

（2）金屬球變為中性。

（3）過程中產生火花。

Which of the following must be correct when a positively charged metal sphere is earthed in the absence of other charged objects?

(1) Positive charges move from the metal sphere to the earth.

(2) The metal sphere becomes neutral.

(3) Sparks are produced in the process.

下列哪些有關電場力線的敘述是正確的？

（1）孤立正電荷的場力線會沿徑向往外指。

（2）場力線的密度代表電場的強度。

（3）場力線可以相交。

Which of the following statements about electric field lines is/are correct?

(1) The field lines of an isolated positive charge point radially outwards.

(2) The density of the field lines represents the strength of the field.

(3) Field lines may cross each other.

一支帶負電的棒移近中性金属球，金屬球置於絕緣支架上。

下列哪些敘述是正確的？

（1）球體的 X 邊出現感生負電荷

（2）質子移到 Y 邊。

（3）球體保持中性

A negatively charged rod is put near an insulated neutral metal sphere. Which of the following statements is/are correct?

(1) Negative charges are induced on side X.

(2) Protons move towards side Y.

(3) The sphere remains neutral.

一支帶負電的棒移近中性金属球，金屬球置於絕緣支架上。

棒的位置維持不變，祖恩觸碰了 Y 邊一下。下列哪些敘述必定是正確的？

（1）電子透過祖恩的身體從球傳到地面。

（2）球體變成帶正電。

（3）球體的淨電荷依然是零。

A negatively charged rod is put near an insulated neutral metal sphere. While the rod remains in position, John touches side Y momentarily. Which of the following statements is/are correct after that?

(1) Electrons are transferred from the sphere to the earth through John's body.

(2) The sphere becomes positively charged.

(3) The net charge on the sphere remains zero.

P，Q，R是三個置於絕緣支架上的金屬球。P和R大小相同，Q則比它們門小。初時，P所帶的電量為 -12 x 10^-9 C，Q和R是中性的。Q先觸碰一碰P，然後再碰一碰R。下列哪一項可能是R最後所帶的電量？

P, Q and R are metal spheres on insulating supports. P and R are of the same size while Q is smaller than them both. At the beginning, P carries a charge of -12 x 10^-9 C while Q and R are electrically neutral. Q momentarily touches P and then R. Which of the following is a possible charge carried by R finally?

圖中顯示點電荷 X 與 Y 周圍的電場圖形。下列哪些敘述必定是正確的？

（1）X 和 Y 帶相反的電荷。

（2）電荷在 ST 上的任何一點都會感受到同一方向的靜電力。（3）置於X 和 Y 中央的電荷不會感受到靜電力。

The field pattern around two point charges X and Y are shown in the figure. Which of the following statements must be correct?

(1) X and Y carry opposite charges.

(2) A charge at any point on ST always experiences an electrostatic force in the same direction.

(3) A charge mid way between X and Y experience no electrostatic force.