Field — Science definition

A model describing the influence an object has in the space around it.

Where it is taught

In use

A field model describes how an object can exert a force on another object at a distance.

Electric & Magnetic Forces

Questions using field

Problem 1

Illustrative tests use the same magnets and orientation with separations 1, 2 and 3 cm. Force magnitudes are 12, 6 and 3 arbitrary units. A paper barrier at 1 cm still gives 12 units. Identify evidence for an interaction across a gap, describe the distance trend and explain why the barrier does not prove a universal field law.
Answer and explanation

The objects affect one another without direct contact and remain coupled across the supplied paper barrier. The measured force decreases with separation in this range. These illustrative records do not establish a universal inverse-square rule for all magnet geometries or show that every barrier behaves like paper. A field is a model of the spatial influence, not a material stream of air.

The objects affect one another without direct contact and remain coupled across the supplied paper barrier. The measured force decreases with separation in this range. These illustrative records do not establish a universal inverse-square rule for all magnet geometries or show that every barrier behaves like paper. A field is a model of the spatial influence, not a material stream of air.

Response criteria

  • Use the supplied conditions and relevant evidence.
  • Explain the scientific mechanism or calculation.
  • State a meaningful limitation or testable next step.

Problem 2

An electric-field arrow at a location points upward. Predict force direction on a positive test charge and on a negative test charge. Explain why both cannot simply follow the same arrow.
Answer and explanation

Positive: upward. Negative: downward. Field direction uses the positive-test-charge convention.

Identify the definition of electric-field direction.

Reverse the force direction for a negative test charge.

Response criteria

  • Name both directions.
  • Explain the sign convention.
  • Distinguish field from a path.

Problem 3

Use the closed-loop and cut-magnet figures. Give the field direction outside and inside a bar magnet, then predict the poles on each cut piece.
Answer and explanation

Outside N to S; inside S to N. Each cut piece has both N and S poles.

Trace a complete loop.

Identify both poles on each smaller magnet.

Response criteria

  • Give both directions.
  • Keep both poles on each piece.
  • Distinguish magnetic poles from electric charge.

Problem 4

Electric field direction: use a positive test chargeElectric field direction: use a positive test chargePositive sourceNegative source+−Field arrow = force direction for a small POSITIVE test charge.A negative test charge feels electric force in the opposite direction.
The blue arrows show electric-field direction, defined by the force on a small positive test charge. They point away from a positive source and toward a negative source. A negative test charge feels force opposite the field arrow. Lines represent a model at many positions, not strings or paths an object must follow. The drawing shows selected directions in a plane, not every field direction in three dimensions.
For this unit’s illustrated case, what does a field drawing help explain?
Answer and explanation

It represents where and in what direction a source can influence suitable test objects. It does not show physical strings or prove identical force at every location.

A magnet can attract a suitable object before touching it. Compare the same objects at different distances. Do not assume every shiny metal is strongly attracted, because magnetic response depends on the material.

It represents where and in what direction a source can influence suitable test objects. It does not show physical strings or prove identical force at every location.

Response criteria

  • Use the named labels, directions or supplied quantities accurately.
  • Connect the visual evidence to the scientific mechanism or calculation.
  • State the relevant model conditions or limitation.

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