Electric Fields (in no particular order)

Revision question

Resistivity

.         (a)     either   (If in parallel) when one bulb fails, other bulbs stay on
or        (If in parallel) can identify which bulb has failed; (1)                                1

  (b)   (i)      P = VI (1)
0.5 = 240 I
I = 2.1 × 10–3 A 1 s.f. in answer (–1) once only (1)                                      2

  (ii)   R = V/I (1)
= 240/(2.1 × 10–3)
= 1.14 × 105 Ω or 1.15 × 105 Ω ans
accept (1.1 to 1.2) × 105 Ω. (1)                                                                  2

  (iii)  A = ρ l / R (1)
= 1.1 × 10–6 × 6.0 × 10–3 / (1.14 × 105) (= 5.79 × 10–14 m2)
A = πr2 (1)
5.79 × 10–14 = πr2 so r = 1.4 × 10–7 m (1)                                                   3

  (iv)  filament too thin / fragile to be manufactured / used without damage;
allow ecf from (iii). (1)                                                                              1

 

         4

[20]

  2.     (a)     current µ p.d / voltage (for a metallic conductor)                                              M1

as long as temperature is constant / physical conditions remain constant             A1

(b)     (i)      (R =)  (= 0.0349)                                                                            B1

(ii)     R =           (Allow any subject  )                                                        C1

                                                      C1

resistivity = 5.6 ´ 10–5                                                                            A1

unit: ohm metre / W m            (Allow V m A–1)                                      A1

(5.6 ´ 10–n without unit or incorrect unit and n ¹ 5 or 3 – can score 2/4)

(5.6 ´ 10–3 W m – can score 3/4)

(5.6 ´ 10–3 W cm – can score 4/4)

[7]

Magnetic Field around a wire

Permanent Magnet Prep

Multiple choice answers

1. D
2. E
3. C
4. A
5. D
6. A
7. A
8. B
9. D

Electric Field answers

Coulomb's Law 2 rods on a balance

Ohm's Law calculations

Ohm's Law

I ampere = I A

I milliamp = I mA           1/1000 A = 10^-3A.

I microamp = I μA          = 1/1 000 000 A =10^-6 A

I volt = I V

I kilovolt = I kV =1 000 V =10³ V

I millivolt = I mV = 1/1000 V = 10³ V

1 ohm = 1Ω

1 kilohm = 1KΩ =10³ kΩ

1 megohm        = 1 MΩ = 1 000 000 Ω = 10⁶Ω

Find the potential difference needed to send a current of 2 μA through a resistor of 4 kΩ

                                    V=IR                 V = p.d. in V

I = current in A = 2μA = 2 x 10^-6A

                                                     R =  resistance in Ω = 4kΩ = 4000Ω

                                    V          = 2 x 10^-6 x 4000

= 8 X 10^-3 V or 8 mV

1 Calculate the current through a resistor of 20 Ω if the potential difference across it is 0.5 V.

2 When a p.d. of 2 V is applied across a resistor the current is 0.1 A. Calculate the value of the resistor?

3 A p.d. of 100 V is applied across a resistor of 2 kΩ. Calculate the current?

4 Calculate the p.d. that will produce a current of 2 mA through a resistor of 4 kΩ?

5 Calculate the value of a resistor if a p.d. of 2 V produces a current of 0.5 μA.

6 Calculate the current through a 1.5 MΩ resistor when a p.d. of 4.5 V is applied.

7 A lamp operated by a 240 V supply takes a current of 0.625 A. Calculate the resistance of the lamp.

8 A coil of very fine copper wire is found to take a current of 0.75 A when a p.d. of 4.5 V is applied. If the wire has a resistance of 1.5 Ω per metre, Calculate length of wire in the coil?

Ohm's Law

I ampere = I A

I milliamp = I mA           1/1000 A = 10^-3A.

I microamp = I μA          = 1/1 000 000 A =10^-6 A

I volt = I V

I kilovolt = I kV =1 000 V =10³ V

I millivolt = I mV = 1/1000 V = 10³ V

1 ohm = 1Ω

1 kilohm = 1KΩ =10³ kΩ

1 megohm        = 1 MΩ = 1 000 000 Ω = 10⁶Ω

Find the potential difference needed to send a current of 2 μA through a resistor of 4 kΩ

                                    V=IR                 V = p.d. in V

I = current in A = 2μA = 2 x 10^-6A

                                                     R =  resistance in Ω = 4kΩ = 4000Ω

                                    V          = 2 x 10^-6 x 4000

= 8 X 10^-3 V or 8 mV

1 Calculate the current through a resistor of 20 Ω if the potential difference across it is 0.5 V.

2 When a p.d. of 2 V is applied across a resistor the current is 0.1 A. Calculate the value of the resistor?

3 A p.d. of 100 V is applied across a resistor of 2 kΩ. Calculate the current?

4 Calculate the p.d. that will produce a current of 2 mA through a resistor of 4 kΩ?

5 Calculate the value of a resistor if a p.d. of 2 V produces a current of 0.5 μA.

6 Calculate the current through a 1.5 MΩ resistor when a p.d. of 4.5 V is applied.

7 A lamp operated by a 240 V supply takes a current of 0.625 A. Calculate the resistance of the lamp.

8 A coil of very fine copper wire is found to take a current of 0.75 A when a p.d. of 4.5 V is applied. If the wire has a resistance of 1.5 Ω per metre, Calculate length of wire in the coil?

SHM Gradient of graph

SHM Calculations with answers

7 Graph with point z

10 SHM graph gradient

tides

Collapsing Tower

Lightning

SHM questions on graphs

Circular motion Answers

Q=It

1.       36C

2.       500s

3.       12A

4.       66 weeks

5.       (i)190mA  (ii) 27 000 C

Stone on String

Conical Pendulum

1 Explanation

There is a resultant (or net or unbalanced) force

􀀹

Plus any 3 of following:-

Direction of motion is changing 􀀹

Velocity is changing 􀀹

Velocity change implies acceleration 􀀹

Force produces acceleration by F = ma (or N2) 􀀹

Force (or acceleration) is towards centre / there is a centripetal

force (or acceleration) / no force (or acceleration) parallel to

motion

􀀹

No work done, so speed is constant 􀀹 Max

3

Motion in a Circle