Electric Field (Concise Notes)
tail of arrow anchored on the point where measurement is done
- Definition
- Invisible force field at any point
- created by a charge or a combination of charges
- exerts a force on any charge placed at the point
- independent of the charge placed at the point
- Representation of Electric Field
- by arrow
- symbol, (overrightarrow E )
- magnitude as well as direction
- magnitude,
- magnitude: ({E} = frac{F}{q})
- also called as electric field intensity
- SI unit (NC^{-1}), (Vm^{-1})
- direction
- along the direction of force acting on a positive charge placed at the point of observation
- (overrightarrow {E} ) at any point due to positive charge is away from the charge
- (overrightarrow E ) at any point due to negative charge is towards the charge
- Definition (mathematically),
- the electric force per unit positive charge
- (overrightarrow {E} = frac{overrightarrow {F}}{q})
- Very small positive electric charge
- too small that it does not affect existing electric field significantly
- represented by ({q_0})
- helpful in finding strength and direction of electric field at any point
- (overrightarrow {E} = frac{overrightarrow {F}}{q_0})
- vector quantity,
- force field,
- exerts a force (overrightarrow{F} = q times (overrightarrow{E})) on a charge (q) placed at the point of (overrightarrow{E})
- transfers momentum and energy both,
- follows superposition principle, (overrightarrow{E_P} = overrightarrow{E_{PA}} + overrightarrow{E_{PB}} +overrightarrow{E_{PC}} )
- Electric Force Method
- Locate the point where (overrightarrow{E}) is to be found
- Put the test charge there
- Identify all the charges that exerts force on the test charge
- Find net force on the test charge using superposition principle
- ELectric Field Method
- Locate the point where (overrightarrow{E})
- Identify all the charges due to which (overrightarrow{E}) is to be found
- Find net electric field using superposition principle
Definition
- imaginary lines
- depicts strength and direction of \(\overrightarrow{E}\) at any point
- tangent to field lines at any point give direction of \(\overrightarrow{E}\) at that point
Features
- originates from positive charge and terminates at negative charge
- in the absence of charges, they extend from or to infinity
- continuous in a charge free region
- density of field lines indicate strength of \(\overrightarrow{E}\)
- denser means stronger
- sparse means weaker
- always perpendicular to the surface of a charged conductor
- never intersect each other
- cannot have two directions at any point
- never makes close loop
