CIE A Level Physics复习笔记9.1.3 Potential Difference

• A cell makes one end of the circuit positive and the other negative. This sets up a potential difference (d) across the circuit
• The potential difference across a component in a circuit is defined as the energy transferred per unit charge flowing from one point to another
• The energy transfer is from electrical energy into other forms
• Potential difference is measured in volts (V). This is the same as a Joule per coulomb (J C^-1)
  • If a bulb has a voltage of 3 V, every coulomb of charge passing through the bulb will lose 3 J of energy
• The potential difference of a power supply connected in series is always shared between all the components in the circuit

The potential difference is the voltage across each component in a circuit

• Potential difference or voltage is measured using a voltmeter
• A voltmeter is always set up in parallel to the component you are measuring the voltage for

Potential difference can be measured by connecting a voltmeter in parallel between two points in a circuit

• The potential difference is defined as the energy transferred per unit charge
• Another measure of energy transfer is work done
• Therefore, potential difference can also be defined as the work done per unit charge

Potential difference is the work done per unit charge

ANSWER:

• Both lamps have the same current, which means charge flows at the same rate in both
• The 240 V lamp has 20 times more voltage than the 12 V lamp
• Voltage is the energy transferred (work done) per unit charge
• This means the energy transferred to each coulomb of charge in the 240 V lamp is 20 times greater than for the 12 V lamp
• This makes the 240 V lamp shine much brighter than the 12 V lamp