Electrical quantities

Question 1

Define electric field

Answer 1

The region of space where an electric charge experience a force due to other charges

Question 2

Define the direction of an electric field at a point

Answer 2

The direction of the force on a positive charge at that point

Question 3

Define electric current

Answer 3

The charge passing a point per unit time, flowing past a particular point in time

Question 4

What is the equation to find electric current

(With units)

Answer 4

I= Q / t

Electric current (A) = charge (C) / time (s)

Question 5

Define conventional current

Answer 5

A current that Flows from positive to negative

Question 6

What is the flow of free electrons in a circuit

Answer 6

From negative to positive

Question 7

What are ammeters used for

Answer 7

To measure current

Question 8

What are the 2 types of ammeters

Answer 8

Analogue - with a needle and scale

Digital- with an electronic reader

Question 9

How are ammeters connected to the circuit

Answer 9

In series

Question 10

What are multimeters used for

Answer 10

Measure:
-Direct current
-Alternative current
-voltage
-resistance

Question 11

What is sensitivity (referring to current)

Answer 11

Response of a device to a change in a current

Question 12

Give 3 differences between direct current and alternating current

Answer 12

In dc electrons flow in one direction while in ac electrons flow changes regularly

In dc ammeter deflects in one direction while in ac, ammeter deflects in both directions about the zero

In dc, batteries produce dc
In ac a generator produced ac (or dc)

Question 13

What does the chemical in the battery produce

Answer 13

• surplus of electrons at one end (negative terminal)
• shortage of electrons at one end (positive terminal)

Question 14

What is electromotive force

Answer 14

E.M.F is the 𝐞𝐥𝐞𝐜𝐭𝐫𝐢𝐜𝐚𝐥 𝐰𝐨𝐫𝐤 𝐝𝐨𝐧𝐞 by the 𝐬𝐨𝐮𝐫𝐜𝐞 in moving 𝐮𝐧𝐢𝐭 𝐜𝐡𝐚𝐫𝐠𝐞 around a 𝐜𝐨𝐦𝐩𝐥𝐞𝐭𝐞 𝐜𝐢𝐫𝐜𝐮𝐢𝐭

Question 15

What is the equation to find emf

Give units

Answer 15

Emf= Work done (by source) / charge

E = W/Q
Units- V=J/C

Question 16

Define Potential Difference

Answer 16

Potential difference is the 𝐰𝐨𝐫𝐤 𝐝𝐨𝐧𝐞 by a 𝐮𝐧𝐢𝐭 𝐜𝐡𝐚𝐫𝐠𝐞 passing through a 𝐜𝐨𝐦𝐩𝐨𝐧𝐞𝐧𝐭

Question 17

Equation for potential difference (with units)

Answer 17

P.D = work done (on a component) / charge

V = W / Q

V - Volts
W - Jouls
Q - Columbs

Question 18

Define emf in terms of pd

Answer 18

𝐄𝐦𝐟 𝐢𝐬 𝐭𝐡𝐞 𝐩𝐝 𝐨𝐟 𝐭𝐡𝐞 𝐩𝐨𝐰𝐞𝐫 𝐬𝐨𝐮𝐫𝐜𝐞 in a circuit of the 𝐯𝐨𝐥𝐭𝐚𝐠𝐞 𝐬𝐮𝐩𝐩𝐥𝐢𝐞𝐝 𝐛𝐲 𝐚 𝐩𝐨𝐰𝐞𝐫 𝐬𝐨𝐮𝐫𝐜𝐞

Question 19

How do you find the charge in coulombs when current in amperes and time in seconds are given.

Answer 19

Current(C) = current(A) x time

Q = I x t

Question 20

How do find work done when pd, current (A) , time are given

Answer 20

Work done (J) = pd (V) x current (A) x time (s)

W= VIt

Question 21

What are the 2 types of errors analogue voltmeters/ ammeters are vulnerable to

Answer 21

Parallel and zero error

Question 22

What should be checked for digital meters before taking readings

Answer 22

Zero errors

Question 23

Define resistance

Answer 23

The opposition of a conductor to current

Question 24

What is the relationship between resistance and current

Answer 24

They are inversely proportional to each other

Resistance⬆️ = current ⬇️

Question 25

What is the relationship between resistance and voltage

Answer 25

They are directly proportional to each other

Resistance⬆️ = voltage. ⬆️

Question 26

Equation for resistance

Answer 26

Resistance (Ω) = pd (V) / current (A)

R = V / I

Question 27

What is ohm

Answer 27

The 𝐫𝐞𝐬𝐢𝐬𝐭𝐚𝐧𝐜𝐞 𝐨𝐟 𝐚 𝐜𝐨𝐧𝐝𝐮𝐜𝐭𝐨𝐫 𝐢𝐧 𝐰𝐡𝐢𝐜𝐡 𝐭𝐡𝐞 𝐜𝐮𝐫𝐫𝐞𝐧𝐭 𝐢𝐬 𝐨𝐧𝐞 𝐚𝐦𝐩𝐞𝐫𝐞 𝐰𝐡𝐞𝐧 𝐯𝐨𝐥𝐭𝐚𝐠𝐞 𝐢𝐭 𝐯𝐨𝐥𝐭 (𝐈𝐕) 𝐢𝐬 𝐚𝐩𝐩𝐥𝐢𝐞𝐝 𝐚𝐜𝐫𝐨𝐬𝐬 𝐢𝐭.

Question 28

What is the ohm’s law

Answer 28

The current through a metallic conductor is directly proportional to the pd across it’s ends if the other conditions (temp.) are constant

Question 29

What are “ohm’s conductors“ or “linear conductors“

Answer 29

Conductors that obey the ohm’s law

Question 30

What is the purpose of rheostat

Answer 30

For changing the current in a circuit