IB Physics SL D.2.6 Electric field strength

Practise finding electric field strength at a point by combining contributions from one or more charges, using distance, direction and superposition correctly.

Exam points

calculate net E at a point by adding or subtracting fields from two charges along the same line
interpret a charge diagram to choose the direction of E at a point midway between unlike or like charges
determine an unknown charge from a resultant E value, keeping distances in metres and units in N C^-1

[Maximum number: 4]

(a)

Define electric field strength.

[ 2 ]

(b)

The diagram shows a pair of horizontal metal plates. Electrons can be deflected vertically using an electric field between the plates.

[ 2 ]

(i)

Calculate the force on an electron between the plates when the electric field strength has a value of $2.5 \times 10^{3} \mathrm{NC}^{-1}$ .

[ 2 ]

$F=2.5 \times 10^{3} \times 1.6 \times 10^{-19}$ ;
$4.0 \times 10^{-16} \mathrm{~N}$ ;

Marking guidance:

Award [2] for a bald correct answer.

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D.2.6—Electric field strength question 1

Question (a)

Question (b)

Question (i)