Resistance II

Question 1

What is the current is resistors in series?

Answer 1

• Resistors in series pass the same current.

* Total pd is equal to the sum of individual potential differences.

Question 2

What is the formula for voltage?

Answer 2

V = I x R

Question 3

What is the formula for total potential difference across two resistors?

Answer 3

V = V1 + V2 = IR1 + IR2…

Question 4

What is the formula for the resistance of resistors in series?

Answer 4

• Total resistance is equal to the sum of individual resistances.
• R = R1 + R2 + R3 + …

Question 5

What is the potential difference of resistors in parallel?

Answer 5

• Resistors in parallel have the same pd.

* The current through a parallel combination of resistors = sum of individual currents

Question 6

What is the current through resistors in parallel?

Answer 6

• The current through a parallel combination of resistors = sum of individual currents

Question 7

What is the formula for the current across resistors in parallel?

Answer 7

P.d. = V
• Current through resistor, R1, I = V / R1
• Current through resistor, R2, I = V / R2

Question 8

What is the formula for current?

Answer 8

I = V / R

Question 9

What is the formula for the total current through resistors in parallel?

Answer 9

I = I1 + I2 = (V / R1) + (V / R2) + …

Question 10

What is the formula for resistance?

Answer 10

R = V / I

Question 11

What is the formula for total resistance of resistors in series?

Answer 11

1 / R = 1 / R1 + 1 / R2 + 1 / R3 + …

Question 12

What is the heating effect of an electric current through a component caused by?

Answer 12

• Resistance of the component.
• Charge carriers repeatedly collide with the positive ions of the conducting material.
• There is a net transfer of energy from the charge carriers to the positive ions as a result of these collisions
• After a charge carrier loses kinetic energy in a collision, the force due to the pd across the material accelerates it until it collides with another positive ion.

Question 13

What is the formula for power?

Answer 13

• P = IV = I^2 x R = V^2 / R

* Energy per second transferred to the component as the thermal energy = I ^ 2 x R

Question 14

What is the formula for rate of heat transfer?

Answer 14

• If component is at a constant temperature, heat transfer to the surroundings takes place at the same rate, therefore:
Rate of heat transfer = I ^ 2 x R

Question 15

What does the temperature rise depend upon?

Answer 15

• If component heats up, its temperature rise depends on the power supplied to it, I^2 x R, and the rate of heat transfer to the surroundings.
• The energy transferred to the object by the electric current, in time, t = power x time = I^2 x R x T

Question 16

What is the formula for energy transferred to an object by electric current?

Answer 16

• Power x Time

* I^2 x R x T

Question 17

What is the formula for power in electrical circuits?

Answer 17

P = V x I

Question 18

What are the alternate formulas for calculating power ( combination of V = IR and P = V x I )?

Answer 18

P = V^2/R
P = I^2 x R

Question 19

What is the formula for energy?

Answer 19

• Energy = Power x Time

* Power = Energy / Time

Question 20

What are some alternate formulas for calculating energy transfer?

Answer 20

• E = (V^2 / R) x Time = Power x Time

* E = I^2 x R x T = Power x Time

Question 21

What is power defined as?

Answer 21

Rate of transfer of energy, measured in watts, where 1 watt is equal to 1 joule per second.

Question 22

How is power derived?

Answer 22

• Potential difference, V = energy transferred •per coulomb
• Current I = number of coulombs transferred per second
• Current x Volume = energy transferred per second = power