iGCSE Physics (0625) 4.2.2 Current-Exam Style Questions- New Syllabus
▶️ Answer/Explanation
Detailed solution:
Statement 1 is correct as electric current is defined as the rate of flow of charge, expressed as $I = \frac{Q}{t}$.
Statement 2 is incorrect because current is measured using an ammeter connected in series, whereas a voltmeter measures potential difference.
Statement 3 is correct because alternating current (a.c.) reverses its direction of flow periodically and continually.
Since statements 1 and 3 are the only accurate descriptions, the correct combination is represented by Option C.
▶️ Answer/Explanation
Detailed solution:
Direct current ($d.c.$) is defined as an electric current that flows consistently in a single direction through a circuit.
In contrast, alternating current ($a.c.$) involves charges that periodically reverse their direction of flow.
While a cell provides $d.c.$, the definition of the current itself refers to the unidirectional movement of charge carriers.
Option $A$ and $B$ describe behaviors inconsistent with $d.c.$, and option $D$ is a specific case rather than a general definition.
Therefore, statement $C$ correctly identifies the fundamental characteristic of direct current.
▶️ Answer/Explanation
Detailed solution:
In a metallic lattice, positive ions are fixed in a regular structure and can only vibrate about fixed positions.
Metals contain “free” or delocalised electrons that are not bound to specific atoms and can move throughout the structure.
An electric current I is defined as the rate of flow of charge, expressed as I= t Q .
In a metal wire, this charge is carried by the movement of these free electrons along the length of the conductor.
While positive charges (atomic nuclei) exist, they do not move along the wire to constitute the current.
Therefore, an electric current in a metal is specifically the net flow of electrons in a particular direction.