# 2.4.4 Fields & Static

### Fields & Static

• Objects with static charge create an electric field in the space around them
• If other charges enter the field then they will experience an electric force, attracting or repelling them from the object
• Therefore, an electric field can be defined as:

A region in which a charged object will experience an electric force

• Electric fields are represented by electric field lines that are always in the direction of positive to negative
• The electric field lines for a charged, isolated sphere, such as a spherical conductor:
• Point away from the centre of a positive sphere
• Point towards the centre of a negative sphere

• A uniform electric field, such as that between two parallel plates, are straight parallel lines from positive to negative:

Electric field lines between two parallel plates

• The electric field pattern between two oppositely charged spheres (or point charges) is slightly different and looks like:

Electric field pattern for two opposite charges

• The electric field helps to explain the non-contact force between charged objects since the electric field cannot be seen, but can be detected by another charged object that moves within that field due to the electric force
• This is a non-contact force because the charged objects do not touch for the force to be exerted
• If an electric field becomes strong enough, the charges are forced through insulators such as air, creating a spark
• This is what happens for example, when a charged person touches a conductor
• The charged particles will travel towards areas with the opposite charge

Positive and negative charges will travel towards the opposite charge, creating a spark

#### Exam Tip

Remember when drawing field lines to always include their direction with arrows pointing in the correct direction. If the field lines are straight, always use a ruler or a straight edge to draw them

### Author: Ashika

Ashika graduated with a first-class Physics degree from Manchester University and, having worked as a software engineer, focused on Physics education, creating engaging content to help students across all levels. Now an experienced GCSE and A Level Physics and Maths tutor, Ashika helps to grow and improve our Physics resources.
Close