Electric Charge and Its Conservation Electric charge is a fundamental property of matter that comes in two forms: positive and negative. The charge carried by a...
Electric charge is a fundamental property of matter that comes in two forms: positive and negative. The charge carried by an electron or proton is an example of a fundamental unit of charge. Charge is always conserved - it cannot be created or destroyed, only transferred between objects.
Electric current is the rate of flow of electric charge. Conventional current is the flow of positive charges, while in metals the charge carriers are actually negatively charged electrons flowing in the opposite direction.
Current (I) is defined as the rate of flow of charge (Q) per unit time (t):
I = Q/t
The SI unit of current is the ampere (A), where 1A = 1 coulomb of charge per second.
Materials can be classified as conductors or insulators based on their ability to allow charge flow. Conductors like metals have delocalized valence electrons that are free to move and carry charge. Insulators like ceramics have tightly bound electrons that cannot move freely.
Circuit diagrams use standard symbols to represent components like batteries, resistors, switches, etc. Circuits follow conventions like current flowing in a closed loop from the positive to negative terminal.
Problem: Calculate the current flowing if 2C of charge passes through a resistor in 5 seconds.
Solution:
Understanding these basics of charge, current, conductors and circuit conventions lays the foundation for more advanced electrical and electronics topics in A Level Physics.