Electronics

Question 1

V =

Answer 1

V = I R

Question 2

A current of one amp is the charge flow of…

Answer 2

One Coulomb per second

1 A = 1 C s^-1

Question 3

Force between two charges F =

Answer 3

F =( Q₁ Q₂ ) / ( 4 π ε_o r² )

Question 4

Force exerted by an electric field F =

Answer 4

F = Q E

Question 5

Electric field created between plates E =

Answer 5

E = V / d

Question 6

Potential energy U, stored by electric charge U =

Answer 6

U = ( Q₁ Q₂ ) / ( 4 π ε_o r)

Question 7

Magnetic field B =

Answer 7

B = ( μ_o I ) / (2 π r)

Question 8

Magnetic field internal B_internal =

Answer 8

B_internal​ = ( μ_o N I ) / L

Question 9

Motion of charged particle in uniform magnetic field… v / r =

Answer 9

v / r = ω = QB / m

Question 10

Motion in a complex magnetic field… r =

Answer 10

r = mv / eB

Question 11

Force between two electric currents F =

Answer 11

F = ( μ_o / 2π ) (L I₁ I₂ / d)

Question 12

Torque on a current loop… τ =

Answer 12

τ = mB sinθ

Question 13

Total resistance in series… R =

Answer 13

R = R₁ + R₂ + R₃ + …

Question 14

Total resistance in parallel… 1 / R =

Answer 14

1/ R = 1/ R₁ + 1/ R₂ + 1/ R₃

Question 15

State Thevenin’s theorem…

Answer 15

Any combination of batteries and resistors with two terminals can be replaced by a single voltage source “e” and a single series resistor “r.”

Question 16

The Thevenin voltage “e” is the…

Answer 16

…Open circut voltage between terminals A and B.

Question 17

The Thevenin resistance “r” is the…

Answer 17

…Resistance seen between terminals A and B when voltage sources are replaced with short circuits.

Question 18

Gain for an open loop Gain_open-loop =

Answer 18

Gain = V_out / V_in = A_o

Question 19

Gain for a closed loop negative feedback…. Gain_{closed-negative} =

Answer 19

Gain = V_out / V_{in =} A_o / (1 + A_oB)

(1 - A_oB) for positive feedback

Question 20

Formula for an inverting Op-Amp… V_out/ V_in =

Answer 20

V_out/ V_in = - R_f / R_in

Question 21

Formula for Summing Amplifier… V_out / R_f =

Answer 21

• ( V₁ / R₁ + V₂ / R₂)

Question 22

The energy between two point charges U =

Answer 22

U = ( Q₁Q₂ )/ 4πε_or

Question 23

Describe the relation between electric potential and potential energy.

Answer 23

Electric potential is the potential energy per unit charge.

Question 24

Define what is meant by power in an electrical circuit?

Answer 24

P[watts] = V I

Question 25

Relationship between resistance R and resistivity ρ of a wire… R =

Answer 25

R = ρL / A

Question 26

State Kirchhoff’s junction rule…

Answer 26

The algerbraic sum of the currents into any junction is zero

Σ I = 0

Question 27

State Kirchhoff’s loop rule…

Answer 27

The algebraic sum of the potential differences in any loop, including those associated with emfs and those of resisitve elements, must equal zero.

Σ V = 0 (valid for any closed loop)

Question 28

State the three fundamental variables which characterise an amplifier

Answer 28

Gain, Input impedance and Output impedance

Question 29

What is the relationship between Power, Resistance and Current?

Answer 29

P = I² R

Question 30

State the vector form of Coulomb’s Law…

Answer 30

F = (( Q₁ Q₂ ) / 4πε_or²) r^{^}

Question 31

Electric field between two plates E =

Answer 31

E = ΔV /d

Question 32

Force on charge in electric field F =

Answer 32

F = q E