PAPER 2 unknown things Flashcards
What is the positive end of a drawn circuit cell?
The end with the longer line
How does the potential difference across two components compare when connected in series and parallel?
Series: p.d. is shared between components
Parallel: p.d. is same across each component
If two resistors are connected in parallel, what can be said about their combined resistance?
It will be less than that of the smallest resistor
If two resistors are connected in series, what can be said about their combined resistance?
It is the sum of both resistors
How can we vary the current of a circuit?
With a variable resistor
What is an ‘Ohmic conductor’?
A conductor for which current and p.d. are directly proportional
- Resistance must remain constant
- Temperature must remain constant
What is the frequency and voltage of the UK mains?
- 230V
- 50Hz
What’s the purpose of the neutral wire?
To complete the circuit, connecting back to the mains supply
Where is the earth wire connected to in metal appliances?
The casing, for if the metal casing becomes live, it will earth the current.
Why is it dangerous to have the earth wire connect to the live wire?
It’d cause electrical surges.
What direction do the field lines point in an electric field and a magnetic field?
In the direction the positive charge would move or the direction the north pole would move.
What is a solenoid?
A coil of wire which makes a strong magnetic field when current passes through.
Describe Fleming’s left hand rule, and what is the name of the effect?
- Index finger: magnetic field direction
- Middle finger: direction of current
- Thumb: direction of force
The motor effect.
What generator produces alternating current and how?
An alternator produces A.C:
- A coil of wire rotates in a magnetic field.
- The end of the coil is connected to commutator rings.
What generator produces direct current and how?
A dynamo produces D.C:
- A coil of wire rotates in a magnetic field.
- The end of the coil is connected to split-ring commutators which change the direction of the current as it changes when spinning, so it always goes in the same direction.
