PHYSICS CIRCUITS

• Circuit


  Any path along which electrons can flow
• Electrons


  • Will only flow if the circuit is complete with no gaps
• Open Circuits


  Broken and do not allow the flow of electrons
• Closed Circuits


  Complete and allow the flow of electrons
• Types of Circuits


  • Series
  • Parallel
• Series Circuits


  • Devices form a single pathway for electrons to flow
• Parallel Circuits


  • Devices form branches, each of which is a separate path for the flow of electrons
• Series Circuits


  • All current passing through each device is the same
  • Ohm's Law (I = V/R) applies to the entire circuit, AND each individual device within the circuit
  • If one device in the circuit fails, the entire circuit will fail
• Parallel Circuits


  • Each device connects the same 2 points in the circuit
  • Voltage is the same across each branch
  • The total current in the circuit is the sum of the currents in each branch
  • More parallel branches = less circuit resistance = MORE CURRENT
  • If one device in the circuit fails, the rest of the circuit still functions
• Schematic Diagrams
• Short Circuit


  • Insulation wears away, causing wires to touch, shortening the circuit
  • This bypasses the normal resistance of the circuit
  • Draws very large currents
• Equivalent Resistance


  The value of the single resistor that would represent the resistance of all of the devices in a circuit
• Combining resistors in a series circuit


  Req = R1 + R2 + R3 + …
• Combining resistors in a parallel circuit


  1/Req = 1/R1 + 1/R2 + 1/R3 …
• Parallel Circuits and Overloading

  • Lines: Low resistance wires connecting wall outlets to generators at the power utility
  • Usually carry 110 V to 120 V
  • When more devices connected in parallel: Resistance is lowered, Current is increased
  • If this current exceeds the safe amount for the line, the circuit is said to be overloaded
  • Resulting heat can melt insulation and cause a fire
• Fuses


  • Devices connected in series to prevent the overloading of circuits
  • A fuse is constructed of a thin wire that will melt if the current becomes to great, therefore breaking the circuit
• Open circuit


  An electrical circuit that is not complete
• Closed circuit


  An electric circuit is a "closed circuit" if it contains a complete path between the positive and negative terminals of its power source
• Resistors in Parallel


  • To determine the current or voltage in a circuit that contains multiple resistors, the total resistance must first be calculated
  • The total resistance is always larger than any individual resistance
  • Since charge has only one path to flow through, the current that passes through each resistor is the same
  • The sum of all potential differences equals the potential difference across the battery
  • Due to this reciprocal relationship, the total resistance is always smaller than any individual resistance
  • Since there is more than one possible path, the current divides itself according to the resistance of each path
  • Smallest resistor = more current passes, Largest resistor = least current passes
  • The voltage across each resistor in a parallel combination is the same
• Personal Protective Equipment (PPE)


  Wearing of PPE is a requirement in the laboratory
• PPE includes


  • Clean laboratory gown
  • Gloves
  • Face mask
  • Head cap
  • Goggles (if needed)
• Only during small group discussion and dry laboratory activities are students allowed not to wear PPE
• Laboratory materials


  • Scissors
  • Masking tape
  • Permanent marker
  • Liquid detergent
  • Hand towel
  • Rags
  • Five amber-colored bottles
  • Match
  • Fifteen vials (30ml)
  • Five wide-mouth containers (60ml)
  • One plastic storage box (6L)
  • Two plastic trays
  • Garbage bags (small)
  • Five whistles
  • Sticker paper
• Pre-laboratory responsibilities


  1. Read the experiment

  2. Understand the rationale

  3. Research Material Safety Data Sheet (MSDS)

  4. Make a schematic diagram

  5. Clean glasswares and apparatus
• Post-laboratory responsibilities


  1. Clean glasswares and apparatus

  2. Dry before returning

  3. Follow first come first serve basis

  4. Place chemicals in respective containers

  5. Maintain cleanliness of work area
• Reservation of chemicals


  1. Reserve chemicals one meeting prior

  2. Fill up chemical reservation slip

  3. Claim chemicals within first 15 minutes

  4. No reservation means no experimentation

  5. Check dispensed chemicals
• Borrowing and returning of glasswares and laboratory apparatus

  1. Reserve apparatus one meeting before

  2. Request using laboratory borrower slip

  3. Fill out necessary information

  4. Submit laboratory baskets with slip

  5. Dispense within first 15 minutes
• Glasswares breakages or apparatus damages in the laboratory should be reported to the instructor and the laboratory-in-charge immediately
• Rules of breakages


  1. Group has one week to replace

  2. After one week, charges to students' account
• Take out apparatus


  1. Obtain take-out apparatus form

  2. Secure duplicate copy

  3. Specify date of return

  4. Charges for late returns
• Chemical waste management


  1. Endorse waste product to instructor

  2. Place chemical wastes in reagent waste bottles

  3. Do not perform unnecessary experimentation

  4. Do not discard chemicals in sink

  5. Reagent bottles provided by stockroom
• Room care


  1. Clean working table

  2. Place garbage in garbage bag

  3. Turn off lights and fans

  4. Dispose used gloves, masks, head caps
• The laboratory can be dangerous if precautions are not taken
• Safety in the laboratory is an emphasis
• Safety rules


  • Wear goggles when required
  • Do not touch chemicals with hands
  • Do not eat or drink
  • Do not taste chemicals
  • Do not smell chemicals directly
  • Do not pipet solutions with mouth
  • Do not put flammable liquids near open flame
  • Direct open tube away when heating
  • Turn off Bunsen burner after use
  • Do not sit on laboratory benches
  • No horseplay
  • Do not pour chemicals into sink
  • Notify instructor of spills
  • Clean broken glass immediately
  • Use fume hood for dangerous chemicals
  • Wash skin contact with chemicals
  • Pour acid into water, not vice versa
  • Experiments under instructor supervision
  • Good housekeeping practices
  • Be cautious and think
  • Know safety equipment location
  • Closed shoes required
  • No unauthorized experiments
  • Avoid rubbing eyes
  • Notify faculty of breakages
• Personal Protective Equipment (PPE)


  • Clean laboratory gown
  • Gloves
  • Face mask
  • Head cap
  • Goggles (if needed)
• Wearing of Personal Protective Equipment (PPE) is a requirement in the laboratory
• No PPE, No experiment
• Students are allowed not to wear PPE only during small group discussion and dry laboratory activities
• Laboratory materials


  • Scissors
  • Masking tape
  • Permanent marker
  • Liquid detergent
  • Hand towel
  • Rags
  • Five amber-colored bottles
  • Match
  • Fifteen vials (30ml)
  • Five wide-mouth containers (60ml)
  • One plastic storage box (6L)
  • Two plastic trays
  • Garbage bags (small)
  • Five whistles
  • Sticker paper